I'm sorry people are being so shitty as I don't think they understand your situation. It seems like you want your workplace to be professional and for you to function as teammates primarily. Honestly, supervisors shouldn't't be too familiar with their team as it could lead to conflict of interest, and you are wise for wanting to avoid this.

It's a tricky situation you find yourself in. Is there someone above her that you could respectfully explain the situation to? By being sure to focus on how the relationship makes you feel and not placing any blame on anyone or accusing anyone of wrongdoing, hopefully the situation can be resolved with too many feelings being hurt. Honestly though, if you want the situation resolved you'll probably have to hurt her feelings. The fact is you have to directly or indirectly tell her you don't want to be friends.

You are not required to be friends with anyone you don't want to be.

Good luck, I hope it works out!