What can I do about my Sister undully influencing my Mother

My Father passed away a little over a month ago. My Sister claims my Dad didnt have a will, and wouldnt let my mother or I see him while in the hospital. She has been arguing w/ Dad while in the hospital. Now she's making my Mother change my Dads accounts, w/ out going through probate. Now she wants my Soc security #.  She is taking control of everything without authority from the court. Mom says she doesnt understand anything about the bank "stuff". Says thats why Sister is doing everything. Sister says nothing goes through probate, cause Mo  owns it all now .  I think she is manipulating Mom into giving her Dads property, and Mom doesnt realize whats really going on. Can you help with this situatio.  Note: FL law changed, and its causing problems. My Sister also has hired an attorney, but I dont think the attorney is working in my Mom's behalf. My Sister has done this once before, whe. my Uncle passed. My Dad wasnt very happy with what she was doing either