Legal Question in Real Estate Law in California

The community may have acquired a pro tanto (meaning for that much) interest to the extent that any community property monies (such as wages or salary during marriage) were used to reduce the debt on the house.

Simple question, but tough to answer. It depends. Contribution of community efforts or money towards the house can create a community interest. This type of issue is what keeps divorce counsel busy. Since this is now a factual matter rather than a legal question, it's unlikely any one can give you a definitive answer. You can get an answer by entering into a properly enforcable marital porperty agreement if your wife is williing to do so. This would require knowledgable counsel (preferably for each of you) and a willing spouse.

Only if she financially contributed to the house payment or improvement.

You'll certainly find out in a divorce, from the court.

In general, if you used any community property income or assets to pay any portion of the house debt or bills, she has a claim that will have to be dealt with.