If the person I owe money to dies, do I still owe the debt?

I borrowed some money from a friend who has recently passed away. I have no relationship with any other of her family members. I did sign an I.O.U to her. It was not notorized. She was very wealthy and most likely had her affairs in order. Her daughter showed up yesterday at my job wanting the money, which I do not have. She said she is bringing an amoritazation(sp?) table next week so I can start making payments to her. Do I owe this money to her? My arrangement was with her mother. Shouldn’t I be paying it to her estate, that is, if I could?