So, the story is short: Her friend is owner of the private elementary school, he wants her as caretaker for holidays (1 month) about 2000 kms away from me. It was her summer part-time job for a while. I don't want her to go, she doesn't want to go either (yet I'm afraid she will accept the offer, when it comes to face-to-face conversation she is very agreemental).

If she goes, I next her. I don't trust her enough, I don't want to be alone for month. Should I confront her with this argument? From my experience ultimatums are bad. I would love your opinion on that matter.

We are together for 8 months, she was a cheater, and very sexual woman. She is insanely in love with me, for those months she never went out or drank without me (I didn't ask her to, she said she doesn't want me to wonder where she is and what is she doing because it would eventually lead me to leaving her).

So she'd be gone for a month? Come on. In my opinion, if she would cheat on you in as little time as one month, she would cheat on you on other occasions too... not gf material.