Talk to your landlord, explain the situation. Landlords have been known to make exceptions in cases like yours. He may reduce the notice requirement to one month or waive it all together. So talk to your landlord first, depending on what he says, plan your next move.

First thing tomorrow morning, separate your finances. Open a new account, and transfer your money. If it's a shared account, she can empty out the account and take all the money. Don't give her the opportunity to screw you over.

Do both of those things, talk to landlord and transfer your money to a new account, BEFORE you talk to her.

She can move in with her affair partner, or he can pay to support her.