Is it normal that...i was annoyed at a guy for talking to my female friend?

Went to my regular sports bar for pizza last night, and, an attractive, widowed blonde, who's older than me but we've become good friends, came in and sat alongside of me. We chatted for a few minutes, if that, and, another guy, whom I've seen here and there and talked to, came over to say hi to her. That became him sitting his ass down next to her and, basically, working on her/chatting her up, no doubt trying to pick her up.

Tuesday is pizza day at the sports bar, and, the only day I see her (maybe the occasional Friday, too), so, when she came in and sat down, I looked forward to what's becoming our usual hangout time. Nothing has happened between us, and we are only friends, but..I was so irritated that the other guy, Bill, took what I saw as MY time with her away, monopolizing her time and attention. Bill did say hi to me as well, so it's not as if he ignored me and directly went after her (although, after he sat down on her other side, that was it for my and Bill's contact..so, he clearly focused on her).

Guess my question is..is it normal to feel offended or annoyed that this guy monopolized her time, essentially, if unintended, keeping her from me? I saw it as something that's just not done, and, even though she and I aren't involved sexually, a kind of..snaking what was mine.

Am I off base here, or, do I have a reason to be a little pissed?