I would listen to what she has to say, occasionally ask her if you can help her in some way, but not otherwise "intervene". Unfortunately you only have her "stories" and they may be exaggerated and are definitely seen through her state of mind/filters. I'm not saying she is lying, only that it is impossible to know/help unless you ask if she would like help and she replies in the affirmative or if she asks you for help herself. I know my husband's first wife has told me stories about him which I'm quite positive are not "true". One can't get into it unless one is literally into it and sees/experiences it first hand I don't think.

Helping another adult with emotional abuse can be a bit of a slippery slope as adults are responsible for their own words/actions and taking that responsibility away from them is an error I think. Poor self esteem is not a good excuse for not protecting one's own boundaries and putting up with something one does not wish to. It's hard to know from our own vantage point whether another perceives their lives/stories the same way we do and what we see as "abuse" may not bother them or may not even be abuse in their context but just sound like abuse to us.

Next time she tells you a story that makes your alarms go off, tell her and ask her if she needs/would like help.