I agree with all the posts above me. The two issues she mentioned themselves wouldn't concern me too much.
However, it has obviously not escaped your attention that she might be attracted to him because she needs a father-figure. So if she breaks up with him, the next man she dates might also be significantly older and/or she might be with him to fill that role.
I think the part that would concern me most would be what PPs have mentioned, that he gave you kind of a creepy vibe and you just didn't care for him. However, you said she's hard to get along with, and she might have a hard time attracting men, so she might just be realistic and might have decided that it's better to be with someone like this man, than alone.
In the end, you have to follow your conscience. I agree with the others that if you do say something, it will very likely end your friendship.
I had a good friend who was in an emotionally abusive relationship. It was very similar to her own parents' very unhappy marriage. I pointed out to her how horribly he treated her, and that it was very much like the dynamic in her parents' marriage. I was hoping to help her realize that she could do better and find someone who wouldn't treat her so poorly. But our friendship ended and she married him anyway. I hope I'm wrong about her husband, but when I spoke up, it was because I wanted to save her from making a miserable and unhappy life for herself. I knew that like her mother, she wouldn't divorce and she'd just endure the abuse. I decided that I'd rather try to prevent her from doing that, and that it was worth the risk because if I said nothing, mine would be the shoulder she was always crying on when he mistreated her, and for my own sanity, I didn't want to put up with that anymore.