You may be able to sue her. It depends on how the money was left. You can visit the probate court in the county where your father died and review his probate file to see how the money was left. The staff at probate court may be able to give you some guidance as to what your mother can and cannot do with the money.
Did Steve Jobs leave his daughter any money?
Lisa Brennan-Jobs, now a 42 year old author and a Harvard graduate, had a different experience growing up with her father than her half-siblings. After his death, Steve Jobs did make sure to leave Lisa with a multi-million dollar inheritance.