Getting Taken advantage of

Okay My friend M is really irrating me. I watched her kids over night on the 6th of this month. So they could do things for the youngests party. Well they didnt do anything so I watched them for no reason appearently. I have watched them alot during the day so they they could go to lunch, get tattos, ect.. They are never on time picking them up, ect.. Well I was suppose to watch then this past Friday but her dh ended up having duty. She asked if I would watch them Saturday Overnight. I said thats fine I didnt have any plans. Well I texted her friday night telling her I didnt think I could watch them saturday because I wasnt feeling good. Saturday afternoon she calls and still asks if I could watch them? Are you serious? I have the flu taking care of my 2 kids is hard enough and you want me to still watch your 3? You know I am sick and you want your kids here? WTH? I told her NO, its woul dhave only been a couple hours but you know in that couple hours I would have had to feed 5 kids, listen to them fight, tattle, and not listen. Her kids are all out brats lately and dont listen. She even admits they are being brats at home and not listening to her or there dad. Yesterday she asked if I would take them this friday overnight. I agreed because I do feel bad about cancling last weekend even though I couldnt prevent it. So I will be watching them late afternoon friday till probably late afternoon Saturday. Today she calls me and asks if I can baby sit for her this afternoon. What do I have door mat written on my face? I am busy and have stuff to do my husband will be home soon. This afternoon I plan on going grocery shopping before kenzie gets out of school that way I only have Kylie to worry abotu at the store (it goes alot faster with 1..lol) So I told her no. I know she was mad but I dont care at this point I think she is taking advantage of me at this point. Sorry just need to vent some