Legal Question in Real Estate Law in California

You are going to have to either buy her out or file an action for partition.

......and if she doesn't respond to questions, filing a partition lawsuit is probably your only logical course of action. As with any lawsuit, you'd need to serve her with the summons and complaint, but that's usually not terribly difficult, especially if you know where the defendant lives.

A partition lawsuit basically asks the court to order the property to be sold, the liens paid, and the net proceeds to be distributed to the (former) owners fairly, after taking into consideration any excess payments one of the owners may have made for things like mortgage payments, insurance premiums, property taxes, necessary repairs, and the like.

Many times, filing a partition suit results in the unwilling co-owner coming to his or her senses and agreeing to an out-of-court settlement of some kind, such as a buy-out or a private, out-of-court sale of the property.

Partition suits are not as common nowadays, with many properties "under water" and unlikely to produce enough net payout to cover the litigation costs, or even to pay off the mortgage, but you might want to discuss the economics and possible outcomes with a lawyer who has done some partitions recently.

The name "partition" comes from the older practice of physically subdividing the property between the unhappy co-owners. Nowadays, that's often impractical because of urbanization and restrictions on subdivision, so in the 20th and 21st Centuries, physical subdivision of land has been largely replaced by court-ordered sale and "subdivision" of the net cash proceeds. The law covering partition actions is found in the Code of Civil Procedure at sections 872.010 to 874.240.