My wife was disgusted by her ex getting semen on and in her, if so why did she not make him wear a?

Some men refuse to wear them. The decision to wear one or not isn't hers alone, but both of theirs.

well if you are new at this kinda thing and didn't know to much it probably happened cause he didn't tell her maybe said it wasn't right if she told him she didn't want this to happen that's where condoms do work sometimes it might have ripped