Am I being too sensitive to the fact the my gf’s friend has come back into her life after 2 years?

My (27M) gf (26F) worked with this guy about 2 years ago. They hit it off pretty quickly and it was clear that he “liked” her pretty much from the beginning. He even kissed her on the lips after a work Halloween party (I was not there). Pretty soon after that he got a new job and moved away, we didn’t hear from him for years. Now all of a sudden he is back in the picture. I’m not entirely sure how they reconnected, but he came over while I was at work this week. That night, as she was telling me about it, she talked about how much she’s adored him and how he was such a genuinely sweet and good person and even how, emotionally, she feels the same about him as she feels about me. Ever since then I’ve been in a pretty deep depression thinking that she would rather be with this guy because, objectively, the two of them seem more compatible than the two of us. Now the two of them are wanting to go out to bars together and are planning all these fun things to do together and she’s constantly texting him.

I hate controlling people, it genuinely gives me the “ick” to even think about telling her I’d rather he not come around anymore, but I’m so afraid he’s going to steal her from me if this continues. Every day with this my mental heath gets worse and worse, I can’t eat and I barely sleep. I even had a dream where I walked in on the two of them in bed together. I love my gf so much and I’d never ever want to do anything to restrict her happiness, but I feel like I can’t go on without saying something. AIO?

Edit: I have expressed some minor concerns to her about him, but whenever I do she takes it too far and is just like “fine, I’ll just never talk to him again” which makes me feel worse because I feel like I’m robbing her of a friend. I don’t even know how to go about expressing my concerns to her without her taking the maximalist route and totally cutting him off when that outcome would make me feel awful and probably lead to some contempt from her side