My gf likes to talk to and have other males as friends. She say that they are just friends and tells me when I question her about it that I am being insecure.
That's the MAIN problem right there. She doesn't say to herself, "My boyfriend doesn't like it when I mingle with male friends. I really love and respect him and don't want to hurt him or lose him, so even though I don't agree with his thinking, I'm gonna cut the cord on these male friends of mine, because my boyfriend is more important. I mean, this is the love of my life I'm talking about!"
Instead, she chides you about being insecure when you make known to her how you feel about this, rather than respect your feelings.
You should've seen this trait of hers before getting into a relationship with her and that's when it should've been handled. Now it's like trying to close the barn door after the cow has left.
The thing to do is not to tell her how you feel but either end things (because this attitude of hers is only the tip of the iceberg and will bite you in other ways as time goes on) or go out and make some new female friends to hang with yourself. See if she doesn't get "insecure".
Guys who become "friends" with women are typically waiting for their chance in her pants. That opportunity comes when she's not too happy in the relationship, doesn't love you as much as she used to.