We studied Freud in one of my Sociology classes in college, but that was 25 years ago. I can recall that some of his theories were interesting, however, I've forgotten them over the years. Maybe I'll read up on those again some evening after my child goes to bed. That would probably be better than surfing social media for a change or watching You Tube videos.

I believe you mentioned that your ex was abused as a child. Did she ever say who the perpetrator was and the age that it occurred? Did she ever receive any type of treatment for it? My ex-g/f was abused by her father's brother from the ages of 6-8. This same uncle abused two of her other siblings, and her parents never got the kids professional help for this abuse. That's where they really failed them. My ex-wife was abused by her mother's brother. She never reported any of this abuse to anyone until after our child was born. While we took her accusations seriously, the age ranges that this abuse occurred in changed at least 3-4 times over course of a few years. First, she stated that the abuse occurred when she was 15-17 years old, then it was 15-21 years, and I think her last accounting of the abuse was age 4 - 21. So none of us knew what to believe. Her stories about several things varied over the years in addition to the abuse allegations.
In regards to triggers, there were periods of time when my ex-g/f would just shut down on me, wouldn't want to talk and wanted to be alone. She appeared to be there physically, but mentally she was checked out almost like she was dissociating. Different things would trigger her when this would happen. When I would ask what was bothering her, she would just say "the abuse when I was a kid and other things from my past. It has nothing to do with you." She leveled with me a few times and said in the past when things like that would come back start haunting her, she'd use alcohol and sex for comfort which allowed her a temporary escape. However, she said "When I was drunk it made me temporarily forget about things. But, the decisions I made when I was drunk were awful." One evening she told me, "Every time I've been intimate with you, it's because I love you and wanted to show you how much I love you. I want to keep it that way because I've used sex as a means for comfort in every relationship I've been in. I don't want our relationship to be like that." She said these types of things on days she was grounded in reality. On the days she wasn't grounded in reality, she was very impulsive, destructive, and irrational. I think our pending engagement also triggered her. She had a fiance before her ex-husband that left her abruptly and devastated her. Based on the stories she told me, it sounded like abruptly broke the engagement because parts of her mental illness were coming out. She kept telling me over and over that she didn't want a repeat of what happened with him and that she hadn't been this in love with anyone since him. I think this is part of why she did what she did with me about 5 weeks later. I also believe her ex-husband's engagement also played a role in our split. That made her spiral out of control even more, then she started blaming him because he deprived her of more children during there marriage. This whole time period was very bizarre and emotionally difficult.
Thanks for allowing me to share my experiences with you. Hope you don't mind. Like you said, "the things we try to understand for them." It sure is mentally exhausting.