Return of security deposit after move out

I have a question about my rental deposit. We called our landlord the day before we called to tell her we were moving and hoping that we could get our deposit back that day. She was very rude and said because we were a few days late on the rent for the month before that she was taking the full 30 days to get it to us. My wife looked online and found something that said she has 21 days. Which one is it? And also, does those days start the day we moved or the last day of the month? We moved out on the 30th of October.