Ex Moved Out of Co-Owned Home, Now Wants Back In

My question involves co-ownership of real estate in the state of: Missouri

My fiance and I bought a semi-rural house together 8-1/2 years ago. Both names are on both the title and the mortgage. She's going through a midlife crisis (52) and decided to (a) move out to a free apartment provided by her employer (don't know what she told them to get that but that charity is ending soon), (b) stop paying the mortgage or any other household expenses although her 27-year-old unemployed son and his pregnant wife are still living rent-free in our basement, (c) quit a good job, and (d) move out of state to buy land, build a house, and have her two sisters do the same and build next to her (a childhood fantasy). She's recently decided to stay in the area and at her job for one year before moving on with steps c and d. She was planning to rent a dog-friendly house. I agreed to buy her out of our house, less my down payment and 6% future realtor commission. She doesn't like that and refuses to sign a quit claim under those terms. She doesn't want to buy me out and own this property herself. I don't think she could qualify for the mortgage. She's now threatening to move back into our basement, hire someone to renovate the basement bathroom to suit her and fence our two-acre front yard for our dogs which she previously took with her to her apartment. The fence was a point of contention before she moved out. She thinks we need it. (We have an invisible dog fence that's been 99% effective for 8-1/2 years when we remember to put the dogs' shock collars on.) I don't want to invest $10K in a fence around our home right now and don't see a need for a physical fence anyway.

The only reasons she would move back in is to save money over renting a house, increase her equity position if teh property appreciates, and push buttons to get her way. She obviously has no affection for me right now. She says she'll be a roommate, nothing more. She hasn't said what roommate status means or what, if anything, she expects to pay. Each email is becoming more confrontational. I don't want her coming back under these conditions. Her current emotional issues are going to ensure a contentious relationship at best. Again, both names are on the title. Is there anything I can do to stop her from moving back in?

You may retain a lawyer to commence litigation for partition and sale of the home, and try to convince a court to issue a temporary order granting you exclusive possession (although I'm not optimistic from what I've heard so far that you would get one). Please note that if your ex-fiancée fights you, you can expect to spend five figures on legal fees and the case could easily take nine to eighteen months to resolve.