Sorry you are here! Unfortunately you have no chance of controlling her. None! No ultimatums, only boundaries. Check legal circumstances. Not married as I understand? As mentioned you can probably not just throw her out. The boundary (if you can’t throw her out) would be to either remove yourself (mentally and/or physically) or initiate real separation/divorce. Don’t tell her parents.
Me: 34 Stbxw: 30 D:5 D:3 Mini bd: May/June 2019 Married: Aug 2019 BD: 6th Dec 2019 OM Confirmed: Feb 2020 March 2020: I filed for D Waiting for D to be finalized and W to move out end of January 2021