How can I trust my girlfriend when she's saying one thing and doing another?

About 4 months ago my girlfriend got a job at a casino. She came home one day telling me how her girlfriends at work was telling her that one of the blackjack dealers have a crush on her. I thought it was funny and so did she as if he never had a chance. Well about a month goes by and we're watching tv and her phone rings and it's him. She didn't answer it and exclaimed that she had no idea why he was calling, but 15 mins later said hE was calling cause he has a friend that repairs body damaged on cars and was needing her car info to get a qoute. I was a little upset cause she lied but again just shrugged it off. Then she goes out with some friends and doesn't at all invite me and that's cool, girls night and I'm okay with that but I find out he's going. So I step up and ask what's going on, I know he has a crush on you and i don't appreciate him hanging out with you when I'm not around. She blows up on me and says he's just a friend he knows I have a boyfriend and would never do anything like that and hes a great guy and really sweet, basically makes me feel like a complete jackass for saying anything. Then about another month goes by and she goes to the lake with friends and hes there but I didn't say anything.Then today he comes to her salon and gets a hair cut and then takes her to lunch! I'm trying not to be mad, I love her very much and I know if I say anything she'll flip it back on me like last time. Idk if I'm different but I don't want another guy taking my girl out anywhere...there's no doubt in my mind he still has a crush on her even though my girl is denying that and saying there just friends. I don't know what to do, Im I supposed to say something again or just stop getting so angry and get over the fact that someother guy is trying to move in on my girl and she's allowing it. We've been together for 7-8 months. Any advice out there would help! Thanks!