Is there an way to fix this love triangle issue?

Alxve

So my girlfriend has an female friend. And that female friend of hers have an boyfriend but it seems like she today sent me an friend request on facebook and told me that "I like you" even knowing the fact that I had an girlfriend. And she said not to tell my girlfriend. My girlfriend and that girl has been in an friendship since kindergarden. Im very much surprised why would her friend try to make me cheat on her own friend? Im stuck on this complex situation. I dont know if I should tell my girlfriend about this or not. Her friend clearly told me not to tell anyone about this and keep it as an secret. Any help from you guys so that I can escape from this situation without hurting anyone?

Is there an way to fix this love triangle issue?
2 Opinion