You would be in a better situation if (a) you had married or (b) you had a contract defining what would happen with your property if you broke up.
As it stands, your instinct is correct - you'll have to sue her, odds are with the help of that lawyer you're consulting (or another lawyer), and a good chunk of the money that might otherwise be in your pocket will go to legal fees. If you can't agree to how to divide any equity in the home, transfer any mortgage liability, or otherwise resolve the dispute over the real property, that could turn into an expensive, protracted lawsuit. For physical property you will need to decide if you are going to request the return of the property, or merely seek money damages - something you can decide after consulting your lawyer. (You can seek the return of the property and money damages to cover culpable damage or for items that are not returned.)

