Betrayed by my closest friend?

So I just found out today that my best friend has had sex with the guy I like more than once. And she's been lying to me about this for over a month. And so has he. And a lot of my other friends.

We've been best friends for over two years and she's lied to me about things a lot. None of them like this though. She's never really betrayed me before.

Do you think we can get past this? And more importantly, should I try to salvage the friendship?