when do i step in?

so im seeing this girl and i suspect one of my friends likes her. he's always texting her at random times during the day (she tells me about all the texts) and he's always inviting himself to things i have planned with her. i dont think he'd try to steal her away from me, but i see it more of a 'setting himself up in case it doesn't work out' with me and her. I try to let it slide and pass it off as nothing, but it does bother me a bit.

i dont know how to talk to him about it (should I?) and i didn't talk to her about it.

i don't know if i'm over reacting or if i'm being jealous or if i have a legitimate thing to worry about.

this sucks.

I don't think you have anything major to worry about, and it's a very good sign about your relationship in general that your girlfriend isn't hiding anything from you.

But I would talk to him and her about it. Let him know that what he is doing is making you uncomfortable, and you would appreciate it if he backed off a little bit. Let her know that you trust her, but explain how this situation makes you feel. Don't get angry at either one, just explain how you feel in a calm, considerate way

If you must speak to him at all, laugh and ask him (lightly) why he is always calling your girl. You can always escalate your response if need be.

First of all, does she answer him? If yes, then that sh#t needs to stop. NOW. Tell her to stop texting him back and if it does not stop she is OUT. Stand up for yourself, you are not a wimp, you have values and opinions and you deserve respect. Would she like it if some really hot girl sent you messages all the time and you responded? I don't think so.
Ask your "friend" why he is doing it and tell him you don't like it. He invites himself to events? WTF? I mean WTF? Your "friend" knows better than that, what a jerk.

yeah, being a controlling asshole is another way to handle it... :D

Just speak to both of them individually about your concern. Tell your friend that you feel uncomfortable when he texts her and invade on you and your girlfriend's alone time. Let your gf know that your best friend's behaviour has been bothering you but you trust her. Remember that a little bit of jealousy is a sign of love; just not too much.