Should I be worried about my girlfriend and her guy friend?

I've been exclusive with a girl now for a few months and I've admittedly been paranoid about her liking her guy friend at university. Recently I've seen a text conversation with him on her phone where she joked that while trying to drive to my house during the holidays she would end up in Leeds where the other guy lives because she has bad navigation skills. The guy then jokes: "see you tomorrow, we could go to a pub you'd like instead" (of her seeing me). Because I think that the other reasons for being paranoid about her liking this guy are maybe irrational, I would like to hear what people think about this conversation. Is it flirty?