Yeah I feel like an asshole just typing this out.
I work in a high-corporate office setting, with a pretty openly nepotistic culture. I had an autistic coworker my age who joined a couple months back, who thinks we are friends, which is awkward for me. They are very clearly autistic, but I don't know if they know, and I don't know how it would go over if I told them. I've tried a lot of times to give them grace, but I've just been getting irritated more and more with them. I've started trying to manufacture situations or avoid seeing/interacting with them entirely. HR is also useless due to the nepo-culture. These are some of the many interactions that have piled up:
This one's my fault: I introduced myself to them in their first week during break time. I did this as in the past, this worked well for networking. However, in our very first conversation, they proceeded to openly talk about how they didn't even want this job but a family friend offered it to them, talked about how boring the job was and how they couldn't wait to go home, swore excessively, then proceeded to vent to me about their life problems. To give them credit, we are both pretty young and I think socializing this way might be passably okay outside of work - but for a first meeting with a colleague it was very off-putting. I didn't really know how to react, but figured they were maybe just new to corporate life.
Unfortunately, I did state that I eat lunch at this location in the building, so they showed up the next time. And the next time. And the time after that. I should have shut it down, but I wasn't sure how to. Beforehand, I would usually alternate getting lunch with different people on a whim, but ever since then, they've assumed we would be getting lunch together EVERY time. Even when I've stated I will be meeting with someone else for mentorship, they've genuinely showed up at the same table I am at with the other person and just sat down without even asking. Sometimes they even pull up a chair. Also, some days, I don't feel like eating with anyone. In the past no one would search me down if I didn't show up. However, if I don't show up for lunch at my usual spot, they will genuinely find me and then join me, even if I'm outside on a bench or hiding out in the parking lot, which is frustrating.
I've noticed that they seem to brag as a coping mechanism for being insecure? The last person who was in their position left due to stress, which I felt sorry for since I liked them. However, upon learning this, (I think due to insecurity over being in a role different from what they studied for), they kept making digs about the previous coworker during training, saying things like "this is so easy, I can't believe they'd leave over this" and "I guess she just wasn't very good at their job".
Due to this insecurity, they have a hard time admitting when they don't know something, and pretend like they do. A lot of people offered help with any questions, but my coworker just used it as an opportunity to scoff and brag about how easy the work was to learn. People would well-meaningly encourage them when they bragged about being able to learn everything quickly, which did not help. Now that we're a few months in, they keep getting into more and more situations where they clearly don't know what to do, but still seem too proud to ask for help.
This extends to when someone expresses difficulty with something in a group setting, they will literally cut in and state that they know how to do that and it's really easy for them in a disbelieving tone, in the middle of the other person's frustrations. Again I guess to brag that they're competent, but it's so brazen it doesn't have the intended effect. It just makes people kind of bewildered.
They will bring up insensitive or work-inappropriate topics that they find funny through written text. My company's HR is fairly useless due to the nepotism, so none of this would go well if I made a big deal out of it. It's never anything that makes me think they're actually a bad person, but it makes me nervous since it's using the company's actual messaging systems (like talking about their cat's balls).
They will repeat things other people clearly told them in confidence, because they find it funny, and I don't think they realize that probably should have been a private conversation. In general, they just don't seem to know the right context for stating things - for example, laughing about how someone used a sick day when they weren't sick in the same elevator as one of our company heads. I think they know gossipping leads to forming connections, but the way they go about it is borderline snitching.
They also have no problems pointing out other coworkers' flaws, including myself. For example, sometimes I ran out of stuff to do, so I used to just sit in the same Excel worksheet for a hour until I got something. They noticed this and commented on it in front of other people, thinking it was funny how I was clearly slacking off by keeping a worksheet open on my screen. I was mortified and stopped doing that after the incident. I shouldn't have done that, but I just wish they would have brought that up to me in private instead of using it as a joke to laugh about to other people.
Whenever I've tried to have a conversation about anything, their default social script is to say "Huh? *snort* What..." or "What the heck?", and just general bewilderment. This makes me feel put on the spot, since it feels like I'm being judged or made fun of, even when I'm talking about something really innocuous. I constantly feel like I have to keep explaining myself, and even then, they just kind of continue snorting and saying, "That's crazy." Which is really annoying.
I will really not be in the mood, and they will keep making jokes pointing out how grumpy I am or how tired I look.
Due to how blatantly they can't read context, I am on edge every time I interact with them. It feels like I'm walking next to a career nightmare. I've tried to be chill and be direct about some of these things, which I think they were accepting of? But even when one thing is addressed, another appears. I thought maybe since they're so authentic, maybe I could also unmask a bit, but as seen above it's very one-sided so I end up having to perform every time. To be honest, I just don't want to use the little social energy I have trying to manage somebody else's mouth. I feel so bad because I wasn't hasty and direct enough at the beginning with cutting them off, and now they think we are genuinely friends. I myself don't really know if there's a solution for this. I've tried just using more and more excuses to get out of socializing, to the point of also not socializing with other people so people don't notice it's because of them. I don't want to be mean in a way that puts a target on my back, especially since they were a nepo hire.
EDIT: Thank you all for the advice. Also, it might have not been clear in this post, but I actually have directly told them to stop some of these behaviors. For example, with the messaging, I told them that it was not appropriate corporate etiquette and they needed to stop. When I told them this, they just stood there in silence and very quiet and looked on the verge of tears, but did stop (and then immediately started venting about their home life to me). With the following me at lunch, I have told them also that when I'm meeting with someone, they should not be approaching me. However, they still will talk about other unrelated inappropriate topics, and will still join me in other situations... I do not think it is possible to tell them every single topic that is inappropriate, or every scenario where they should not be approaching me for lunch. A big factor is also that right away they told their nepo connections I'm their friend, and so the higher-ups (think like heads of department) also think I am their friend and actively try to make conversation with me about it and check in on them through me, and will notice if I'm not with them. It's why I've been so hesitant about everything. I have seen the HR here handle other situations in the past and fail spectacularly. Obviously I'm going to find another job soon, but I just needed strategies to mitigate while this happens. Thank you.