She works with a man and always looks at guys that check her out.
I wonder if you are having some of these thoughts related to something that has neither happened directly to you in your past or to someone that you care about. This can often change the way that we look at different situations. Try to look at what feelings, for you when you notice that someone is "checking her out," and perhaps when you have felt these feelings before.If you trust your girl enough to have an open conversation, perhaps you could ask her whether she is willing to talk about something that is important to you. Then you could talk about feelings that you're having.