Is it normal to be worried other guys might try something?

i don't think she's doing all of this on purpose. if she didn't want you to know whay she was laughing and who she was talking to she could have simply lied and said a girl's name instead of those guys. i think it's just a coincidence that she always happens to be talking to a guy. and i know that it hurts when she said "tom said he loves me n stuff", but she was trying to be honest, which is good. it's good that you trust her, be patient, even though it's a little hard to be. you could do the same things though, while she talks to you on msn, you be unresponsive too and say "oh im just talking to my friend.." a girl's name, that would get her kinda jealous and if you keep doing it she's gonna realize what she's doing is messing you up so she's gonna try not to talk to as many guys anymore.