I put my wife on the deed a few years ago during a simple refinancing of the existing mortgage, for survivorship reasons. I had owned the home for 10 years prior. Now she wants a divorce and half the home's equity.
Do the personal property going into the marriage rules still apply, or is it now community property?

What if my wife made me sign her on the deed under duress during the re-financing process?

now she owns half of the house since you added her.

duress, she held a gun to your head ? Please you did it to keep her happy. And really messed up.
Did you have any prenups signed about property you owned ?

But most likely the court will give her some value of the house, time for an attorney and try to work out something though mediation.