I don’t like her romantically and want nothing sexual with her either. She acts desperate to talk to me, won’t get into more details.
I could act busy each time she approaches me, and avoid her as much as I can but I don’t know if I should tell my manager about this. I don’t even know what I’d tell a manager: “I’m informing that I want nothing to do with X and I’m going to keep my conversations with her to a minimum”?
Another idea: be boring as f*ck.
Do I tell her friends I don’t like her?
Ideally I could tell her directly I’m not interested / I don’t befriend coworkers (not true but it would work to soften the blow), but I simply don’t know how defensive she’s gonna get, laugh it off or accuse me of playing games.
Tell her this “I feel like you want to tell me something, but you’re not saying it. What is it? Your behavior towards me hasn’t been usual.” If she says she wants to be your girlfriend, just tell her that you’re not interested. If you’re just trying to avoid her, she will keep trying until she succeeds. When she realizes that she won’t have anything with you, she will only feel worse for having wasted her time. It’s better to be direct rather than indifferent.