What is the statute of Limitations to file a lawsuit on an overpayment of $400k in est.final profits on the dissolution in 2007 ? It was a CA S-Corp.

I started the company in 1987 and hired my sister who I ended up gifting 10% in ''94 and 23.33% more in 2006. We intended on retiring in 2007, and dissolved as planned. She was persistant on collecting her share of retained profits and our CPA was slow on giving final numbers, so I wrote her a check for "estimated final disbursement" that turned out to be $405,000 too much. We agreed at that time that an adjustment would be made when we received the info from our CPA. She paid me $100k as good will in 8/2010, and started auditing records because she could not believe the final numbers. She has never paid attention to the financials, and does not understand them. She claims she discovered expenses that were mine and they were personal in nature, and she should get credit. My problem is I gave her the shares to give her fin''l security,, not in lieu of any debt or wages etc. She accepted it at the value established at the time.. I proposed a settlement but she is not responding.