I consider it a red flag if someone starts talking about their exes to you early on. To me it's a sign that they are still focused on the past and not yet ready to move onward. Just agreeing with you that it's not quite appropriate first date material. Well at the very least it's awkward.

I personally never bring up my past issues, mental health issues, etc with people until after I have had some time to get to know them. I don't want to come across as like I want them to pity me (because I hate that), and I also want a chance to show them basically "this is me" and not, "Hi my name is MENTAL ILLNESS." Combination of those two factors.

Also you never know what that ex of hers was really about. Some people engage in bad, abusive behaviors and then try to use the pity play and claim to have mental illness when they don't, making a bad name for and creating misunderstanding about those of us who do have mental illness. I actually knew a guy a couple years ago who claimed to have bipolar disorder and didn't have medication for it. But he was actually just an ***hole. Lying all the time, passive-aggressive, trash talking everyone behind their backs, manipulative, just slimy. Never seemed to have any bipolar-specific symptoms to me. But he sure loved to blame it on BP whenever someone called him out on the slimy behaviors.