Your mom's policy should give you a pretty good idea. You'll have a deductible (you have to meet this before the insurance pays) and/or co-pay (you have to pay this portion of the stay), usually with a maximum out-of-pocket (anything over that amount you don't have to pay anything). So you may have a deductible of say $1500, a co-pay of $200/day and a maximum out of pocket of $2000.

Until you hit $1500 it's all out of pocket. Once you hit that you will pay $200/day until you hit $2000 and then you don't have to pay anything more.

Try not to worry about the money; you need to get the help you need. THe money will work itself out. You need to get things under control; that's much more important.