im sorry, but supposed you tell her husband and he kicks her out or whatever.. do you REALLY think she'll come running back to you? Right now maybe she doesn't hate you, but if you ruin her life, she will. If you care about her soo much to want her friendship, can you tolerate her hating you? Also the fact that whilst you might be successful in ruining her relationship, you think she'd want to to go back to you and spend the rest of her life with someone like that? By the way, it is NOT your job/duty (whatever you call it) to tell her husband about her past. A good Muslim is one who puts pardah on another Muslims flaw/sin/gunah (even though I don't think she did any!!) . My two cents for the two brain cells floating in that akhrot dimagh of yours.
now thats what i call a perfect description of this guy ... well described ... :D