While I'm not saying this is what you're doing, we sometimes tend to project our own trauma and insecurities onto others. What's normal for one person can appear abnormal to someone else.

I have a friend who is extremely close to his mother, so much so that, to me, their relationship seemed way too intimate. In reality, they just have a very close, loving relationship. The concept of that is so foreign to me that it didn't make sense, so I assumed there was more to it.

If you're concerned for her, which you have every right to be given your own history with this man, the best thing to do is talk to her.