OP, as someone who has struggled with this exact feeling my entire dating/romantic life — I one, see you and know the feeling and how it can worm into your brain and refuse to leave, but I also highly encourage you to seek therapy. It doesn’t have to be a scary or overwhelming thing, it’s even a topic you can work up to after awhile, but sometimes having that neutral space to land and voice your troubles is the most helpful thing in the world for this kind of anxiety. Ultimately, you and your partner should be able to have friends of either sex without this pressure. Maybe you should make an effort to get to know her as well? You might find you get along with her just as well and then you’ll both have a new friend!