Neighbor I babysit for blames me for everything and never her kids the perfect angels? HELP PLEASE?

ok i know that I have to watch them and all and it gets so hard. I'm 15 and I babysit a ADHD 8 year old girl, and her half brother who is 5. Here's where it gets bad the mom never gives her child her medication unless she is going to school that day so I have to babysit her when she is unmedicated. So needless to say she is bouncing off the walls all day, and she likes to get into everything. Now the boy he has speech problems and its hard to understand what he is saying and he is almost as bad as his sister but he is easier to control. What irks me though is I now can never have any of my friends over cause I have to babysit everyday I had to give up MY summer break to watch her kids everyday and you know what I didn't get paid. This isn't the first time I've babysitted them and never got paid. I've been babysitting them since I was 13 and in all that time i've been paid twice, and sometimes their mom will give me chips and cheese from the mexican restaurant her husband works at, and that is how she pays me occasionally. So moving on, yesterday I walked in that house to babysit and the husband was just standing there as the kids had poured glitter all over the kitchen table, wrote all over themselves in marker, wrote on their board games, and the kitchen floor. So once the husband left I took the nail studio that they got the glitter from and put it up then cleaned the glitter up. They got some chips out to eat while watching cartoons, and then they asked to play with play-dough I said ok then they got some out and was sitting in the living room with it. Well I couldn't stand it much longer because they kept throwing temper tantrums so when my mom got home from work she took care of them until the mom got home. After the mom got home she complained and b***hed at me cause the house was in ruins. The husband then had the nerve to say "It wasn't like this when I left" and p-ed me off. Then my mom went over there to talk to her and the lady said "Well a 15 year old should be able to control an 8 year old." My mom then told me what she said and that lady can't control her own daughter how am i supposed to. Then the 8 year old decided a good lie wouldn't hurt and told her mom that i pull her by her arms all the time (I've never touched her arm unless it was to stop her from running or help her up when she trips). My mom then said she's going to go to the school and ask for one of those papers that allow a 15 year old to work, because I told her the truth and this is one of the normal days.

P.S. I'm sorry about making it so long but I just ranted for awhile so sorry if you don't like them long and should I stop baybsitting for them and i'm babysitting them today cause she can't find anyone who will put up with them for as long as I have and she's also lucky I don't say pay me when she doesn't she's payed me twice and those equal up to $100