Legal Question in Wills and Trusts in California

Not unless it was a loan with a signed promissory note, or if there is a provision in your parents' Wills or trust to offset the gift against your sister's share.

So long as your mother had the requisite legal capacity then it is her prerogative to gift whatever money or property to whomever she wants. Unless your parent's will/trust contains a provision that provides that a beneficiary must repay, from that beneficiary's share, any lifetime gifts or loans, then these funds cannot be deducted from your sister's share.

I disagree with the previous responses.

California recognizes a general legal principle known as ademption by satisfaction. That satisfaction can be shown by an inter vivos gift. A specific, general, or demonstrative gift may be satisfied in whole or in part by an inter vivos transfer from the testator to the beneficiary after the execution of th will, if the testator (the one preparing the will who is planning for their estate to pass at their death) intends the transfer to have that effect. This doctrine does not apply to gifts made before the will.

California Probate Code section 21135 requires either that (1) the testator's intent be expressed in a contemporaneous writing stating that the gift is to be deducted from the devise in the will or in satisfaction of the devise, OR (2) the donee acknowledge in writing that the gift is in satisfaction of his rights under the will, OR (3) the will itself provides for deduction of the lifetime gift.

Thus, I disagree with the previous responses, because they assume that the evidence can only be in the will. The evidence of the gift must be in writing, but it does not have to be in the will itself.