Legal Question in Wills and Trusts in California

It may not be too late, but it is not possible to say definitively.

The statute of limitations is a bit complex in trust matters. Assuming you never received a trust accounting, your statute of limitations is four years from the wrongful act. The statute may be longer or shorter than that, depending on other factors, like whether you received an accounting, or whether the statute was extended because of what your sister told you about when you'd receive your money. It's impossible to say, however, when the statute of limitations period began, except that it almost certainly did not start at the time of your mother's passing.

The other issue is whether your sister has spent the money that you claim belongs to you. If she did and there's nothing to collect, there's not much you can do.

You therefore need to find legal help right away. You can look through the list of attorneys here on LawGuru. You can contact your local bar association. There are other sites that provide connections to attorney who handle claims on behalf of beneficiaries.