In terms of your two questions, I think a way to hold both possibilities in your mind without stressing too much is to try to focus on the fact that whatever happens is entirely out of your hands and that holding a lot of worry around something that you have no control over isn't helpful for you. I realize that knowing a thought pattern isn't helpful and actually stopping that thought pattern are very different things, but if you find yourself really caught up in wondering what will happen with her, I think it may help to say to yourself (even out loud, if you're alone!) "It's not up to me what happens, and I want to focus on things I can actively do for myself" and then try and redirect your mental or physical energy into something positive and active.
If you want to try not to talk about this and your feelings about being single too much to other people, this is what keeping a private journal or other personal writing space is great for! You could even give yourself a set amount of time to write every day, so that you don't run the risk of putting too much time into it, but this could be a space for you to be as longwinded and in-your-feelings as you want without worrying about what anyone else thinks about it.
I don't think this is something you can't talk about to other people at all, but if you feel like it's all you can talk about, or if anyone's asked if they can talk about this with you less, having that private space to process your feelings will hopefully help.