Mom put my sister on her checking account (joint acct). Mom died and left a good deal of money in acct. My sister ended up with my mother's money since banker told her it was hers (joint checking acct). In meantime, found an unsecured bank loan mother had made to grandson, about $15K outstanding and a hospital bill unpaid - $3K. Is my sister responsible to pay these bills from the joint checking account monies she took over?