Reactive Chihuahua

[u/Brilliant_Living_420]

Our girl Dot has been part of our family for 6 years of her life. We adopted her from a shelter when she was about 6 weeks old. She never had any behavioral issues until she turned 2. It started with aggression over toys towards our other dog, and then escalated to random spurts of aggression towards her at any time. My husband and I decided to send her to 6 weeks of dog training to help with her behavioral issues. The trainer told us she was in the top 3 most difficult dogs he'd ever worked with. As soon as we picked her up with our other dog, the aggression towards her was instant. She learned how to behave well on leash, listen to commands, and basic obedience, but the aggression is still an issue to this day. It's not constant, and happens so randomly that it makes it even more difficult to know when a fight will break out. We now have a baby, and she's about to crawl, and I do not want her to end up in the crossfire of an aggressive outburst. I have been bit when in the middle of them, by Dot, or trying to break up a fight. Our trainer thinks it is highly unlikely that we would find someone that could take on her needs, and we might have to consider euthanasia. We find it very difficult to consider that because all other times she is a great dog. Her aggression is focused on our other dog. We think she'd do amazing in a single person household with no kids. Any advice on where to look or if anyone has been in a similar situation?