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.
I would tread very carefully. If she just seems interested but doesn’t cross the line into stalking territory, I would do nothing to confront her about it. If she doesn’t take it well and goes to HR as an unrequited love revenge move, you’ll be sitting in unnecessary hot water. You can do everything right and still lose.
Treat her neutrally. If you can send down the office grapevine how you’re interested in this person outside the office, that’s about as aggressive as I would get. Try and keep a physical distance. Discourage physical contact and avoid situations where you’re alone with her.