Should i just let it p although it pissed me off?

some girl from my bf's myspace added me and is being friendly to me but my bf doesnt like her because he said she can be annoying, he already blocked her on msn because she bothers him a lot even when on busy status. but in fairness this girl is friendly so im just being friendly also, she has a bf and left nice comments on my pic together with my bf. i thought they're really friends because i often see her posting comments on my bf's account and same as he did so when this girl told me she lost her phone and my bf's number and asked for it, i gave it because he already did gave her his number in the first place and i was trying to psych him a little to read more of his ways before we became official. so as our conversation goes, i found out that he lied to me saying he doesnt give away his number just to anyone, but turned out that he did before with not just one, but quite a number of girls from his myspace. he already bought a ticket for our holiday in paris but im still pissed