Am I overreacting in the future?

​

So I am getting ready for an upcoming situation that is coming up. My ( 54) GF (58) has a male admirer who is coming into town two days from now amd he will be staying for two days. My Gf works at a university Archive and he has scheduled some tome to come do some research and she will jave to help him. So let me ask you this.

Am I over reacting to not wanting her to go out to lunch with him. Note: he has expressed his fondness for her in several ways even physically but it was before she and I were together. We have only been together 6 months. ?