Maybe it's because she's been abused by him. In her other life she wasn't able to fight so maybe when facing her "past lover", she still sees herself as a weak woman who can do nothing against that mad man.
Y’all don’t take mental health seriously enough and lack empathy for these characters
I don’t think it’s weird at all. Like other comments said, it’s deep trauma from her previous life. Plus, she’s mentioned several times that even if she is stronger in this life, her human body can’t handle her original power. So she’s essentially level capped rn in her current body. We also haven’t seen her test her current body’s power limit, so she also doesn’t know how strong she actually is and can be right now.
It's kinda weird that she's quite strong but all he thinks about is running away