My mother passed last year and we are now concluding the trust…

My mother passed last year and we are now concluding the trust she left to my sister and my self. Originally, my mom was receiving deposits into her checking account for 3,000.00 from her stocks. The checking account was, unfortunately, not included in the trust. My mom thought it was but she did not change the bank papers. So, it went to my sister as her name was on the account. I understand the funds are now hers and am resigned that she went against moms wished. There was 17,000.00 in the account.

The problem is that after my mom passed the funds were still sent to the account even though the bank where the trust was kept was given a death certificate and told to stop sending funds. The trustee did not know the funds were being sent to my sisters account and now that everything is concluding the taxman has discovered that 33,000.00 erroneously went to my sister. She refuses to return the funds (1/2 would be mine). The trustee has 8,000.00 in the estate account and will give those funds to me but I will be out the funds sent to my sister (12,500.00).

I need to add that the trustee is my sister's daughter but it is my belief that she did not know what her mother did. My sister is not a good person and will not care that her daughter has been put in a difficult position. My question is: Can I retrieve the funds legally?

Thank you so much, Donna