<human>: She and I are early twenties while the 'friend' is mid twenties. I've been dating her for 4 years, she's known the 'friend' for two years, maybe more.

Last night he took her out for dinner and then they went back to her place for a movie; he left at 2am. She met me after work today, why she couldn't tell me this earlier I don't fucking know, and said he flirted with her the whole night. He held her hand until she ordered him to let go, and tried to lean her in during the movie, for a kiss or a hug I don't fucking know. She has *never* given me a reason not to trust her. I want to marry her, and he knows this yet he says our relationship is going to implode in the end.

Should I be mad? Should I not have her see him unless I'm there? What is up with this guy?

Provide a brief overview of the text.
<bot>: Girlfriend went on a dinner and a movie date with a 'friend' which resulted in a flirtatious night. Should I tolerate this bullshit, or not?