Well You are a Great mother.
I'm also glad that she is getting this child support, but how dare her take from your pocket when you have your own family to take care of.
If this was me I would have told her that if your old enough to play the grown up game then your old enough to be responsible, and she should have had a job for the last two years to pay for the babies needs, you are responsible for her but she is responsible for the baby. The end.
But since you are a wonderful parent,things are diffrent. I would not give her anymore money. You have a month or so until you are no longer responsible for her. Since she toke advantage of you, you have no resposibility to her. Let her know that you found the check and she needs to pay for things herself, and that when she is 18 or September 1st she will need to leave or start paying rent for the 2 of them to continue living their. Let her know that you have always been their for her and you are hurt that she has taken advantage of you. Tell her and give her a list of the things that she will be responsible for like:
1. $200.00 rent-this covers a roof over your head and food
(you decide what it covers & how much & when it's due).
2. to live here for $200.00 you are responsible for, dishes
3 nights a week, vacuuming the house twice a week and so on.(you decide what she sould be responsible for to help you out).
3. you need a job and a sitter. I don't do it for free unless I decide that this time I'll do it for free. I'll let you know before I baby sit.
4. I am not responsilbe for your baby when your to lazy to get up and take care of it. Your the parent you get to do it.
Think about your list for a few days and change it if you need to. But you need to make her responsilbe, Tough love for this one. Remember she is the one that toke advantage of you first, and you don't even know for how long.
Love goes both ways, one can't always be the giver, someone has to refill the candy jar right. If she is going to treat you this way then you treat her the same way until she catches on that it sucks, and starts treating you better. When my kids tell me no, I don't want to. Or they just don't do what I asked. That's when I start giving it right back to them. (mom I need you to take me to susies? That's nice but I don't want to.)they have to find another way to get their.
I think that if you make her be a grown up and start paying for her own things she will become a great person. She sees you as a great roll model, for taking care of her and her child, But she won't tell you that until she is out on her own. I know it's your grand baby and you love them dearly, but at 18 she needs to figure out life like the rest of us. Good Luck! J.