Definitely not okay. She should respect how you feel. It’s not anything out of the ordinary to feel the way you feel about it especially if you love her and want a future together. If she cares about the relationship and your feelings she would be able to let go of the friendships she has with these guys. She obviously has liked them in a sexual way in the past, how do you know she doesn’t now? It doesn’t matter how great of a person she is. It is downright disrespectful that she thinks it’s okay to keep seeing those “friends”. She should at least tell you you can go too if she hangs out with them. If she isn’t even trying to invite you when she hangs out with them that is even more sketchy.