You may have hit on the real issue

After only 8 months of being together the real issue is his past. She said the other woman and her bf's past with her really bother her.

Depending on the age of the people involved here, unless they are very young, it is unlikely to find too many people who don't have some kind of a past - especially a sexual past. I know from my own experience that a person who has a lot of love and sex in their past can be difficult to deal with. Particularly if they like to talk about it!

On the flip side of the issue, I moved from a relationship with someone who had a lot of romantic and sexual experience and liked to talk about it alot to someone who had very little of that type of history and experience. Sometimes I wonder if he should have experienced more in the past so he could know himself better and make better choices - instead of just taking what "fell into his lap".

My point is that sooner or later suspicious people (yes - me!) will start worrying about the past, no matter what it is. She has to learn to differentiate between whether this is truly a past relationship or an ongoing one. That could take a little bit of time to figure out. There is some risk involved in being with a person who has had children with someone else and that is always obvious from the outset. There are some people out there who are very good at handling joint custody and past relationships. That could be a good sign for the new relationship, because they have learned a lot and try hard to be rational and emotionally stable.

She just has to observe and give the relationship time to truly identify itself.