so there's these 2 guys, used to be best friends long time ago, as time passed they gradually stopped hanging out and stuff, called each other like twice per months to these small 5 min talks about how's each other's life etc. After some time one of them happens to get some girlfriend and they be together for like a year. Point is She is not happy with him, at least not as happy as a girl is supposed to be in a relation ship with someone she's supposed to love. It also happens that this girl meets her bf's ex-bestfriend and realises she likes him way more, feels he is more suitable for her. So she actually quits her bf and make all she can do to make up with that other guy, which does approve her and they start to go out, gradually getting in love.
Question is, since that's pretty much subjective, what is your opinion about the fact that that new guy started to go out with his ex-bff's girlfriend? Should he say no to her and just ignore her? (Assuming he liked her a lot of course). How right and/or wrong you think that is?