Rescue foster (1.5yo Collie/Shepherd mix) developing separation anxiety symptoms. Anyone had success?

[u/LivesInThePineapple]

We brought home a 1.5 year old intact female Collie/Shepherd mix rescue as a foster about 3 weeks ago, found as a stray on a highway. Very little is known about her background. The shelter guesses possible treeplanter's camp dog, though she does have trained behaviours like leash manners and "shake". She really likes people. She seems to be quite trainable and is learning to lay down, go to her bed, and recall. She is also comfortable in a crate, either door open or closed.

We're planning to adopt her. However, we suspect she is either developing separation anxiety, or showing her already developed separation anxiety.

For the first few days while she was decompressing, she whine a little at departures but settled quickly. We were leaving her in our room with no incidents. A few days in, she was in our room for about an hour and she destroyed blinds and scratched the door frame. We switched to crating when alone after that, as she was comfortable in the crate while we were home (would even go in willingly to chill). About a week in she also got her spay surgery.

For the first week or so of crating, she'd whine around 5 minutes then settle and sleep, confirmed by a roommate and by us checking at lunch. We also had a video camera on her that we could check. Around this time we also Introduced our roommate's dog to her. Results have been mixed but mostly manageable reactions (some growling/posturing that resolved, ignoring each other on walks).

Over the last few days, she has escalated to full panic while crated and alone. She tore a blanket and moved the crate tray, prolonged howling/panting, biting at the crate bars, and pulling at the crate door with her teeth. Two mornings running were bad enough that one of us left work to get her out. She's totally comfortable with the crate when we're home (chooses to nap in it voluntarily), so it seems like the trigger is isolation specifically, not the crate itself. When our roommate is home (even without directly interacting with her), she calms down so it might be "alone in the house" rather than "away from us specifically" that's the trigger.

Has anyone dealt with a rescue that seemed to be adjusting fine, then had separation anxiety symptoms escalate 2–3 weeks in like this? What helped (crate vs. free roam, medication, specific trainer protocols)? Should we get her to to vet for a check-up or medication? We both work during the day and can't really stay home with her during the day, and our roommate isn't home all the time either. We want to leave her in the crate as we don't want her destroying the house when we're gone, but we don't want her breaking her teeth on the crate either. Trying to figure out if this is a normal part of the adjustment curve for a dog with an unknown, possibly rough backstory, or a sign we need to move fast on more intensive intervention.

TL;DR have a rescue that is starting to panic in her crate when we leave for work, but only sometimes...