well once someone steps out of the relationship than there is no point in it after that but fer v me ta puchanga k edan karn da reason ki aa.reason te depend karda v maafi ditti javegi ja nahi. If im the reason like lets say if i dont give her enough time, attn etc and she steps out of the relationship than i guess me usnu maaf kardevanga but again sara kuch depend karda situation te and it all depends on kehri hadh tak gai if u guys knw wat i mean.
I would just tell her that the relationship is over and she has broken my heart. No fighting, but just a little, calm & emotional speech will do the work. If she understands, then it's fine. If not, that's fine too.