I don't want my boyfriend to spend time with another girl. I feel that's unacceptable.
Why? You don't trust him?
Well, she gives out negative vibes
That's not an acceptable reason to stop your boyfriend from hanging out with someone. That's a baseless assumption.
He'll learn it's not ok to cheat on me.
You're just assuming he's cheating when you don't know anything. You need to stop being so controlling.