no there is no reason for that.
even if i have a gf then i wont give up the friendship with my other female friends.
friends is friends and girlfriend is girlfriend.
it depends, if i don't love my boyfriend and loves the other one then maybe just maybe i would go for the other one, but if i love my boyfriend, then who cares he's jsut a long lost crush anyway!
and i don't know if that person loves me back or not, so why should i sacrifice my relationship to that guy if i don't have an assurance that he loves me too or not?.
If you are in a committed relationship, it's not a good idea to go out with people of the opposite sex, or to have a "friends" relationship, like phone calls, e-mails, etc. It's detrimental to your committed relationship.