10 kids for 1 adult at Home Daycare Center?
I would not feel comfortable at all with a child to caretaker ratio that high. In my state, the max ratio is 10:1 for preschool and kindergarten age, 7:1 for toddlers between 1 and 2 1/2 years, and 4:1 for infants. If there are 2 kids under age 2 and the home caretaker has more than 7 kids, or there are more than 10 kids of any age, they HAVE to hire an assistant and both caretaker and assistant must be appropriately credentialed. That tally still applies even if some of the children belong to the caretaker or any assistants they hire.
If you are being serious here, that is not a legal adult to child ratio for a child care operation be it privately or professionally run. How could you consider that safe? An 11 to 1 ratio? How would that work with the woman having children of her own while trying to manage all the others. Things will not be smoothly run, it isn't legal or safe.
My wife has 8 kids in her DC / Preschool, 2 of those are infants, that's is the max allowed by our state for one teacher. She does a great job, and they've all placed well when testing for kindergarten. She has no problem giving them all plenty of attention. For field trips, she'll ask a parent or our daughter to assist her.
Make sure she is licensed by the state. In my state the licensed child care provider can have no more than 10 children under the age of 13, including those blood related, to stay in legal compliance with only one adult caregiver. In addition there are further limitations about how many of each age that consist of the maximum 10, for example the limit is 4 for children less than 12 months. You can listen to the law, your gut or your wallet, but generally speaking I suggest you prioritize your gut when considering entrusting another with your child.
How old is your child, and what are the ratios for your county? (James has a great link on federal ratios, but many counties have ratios even lower than that.) If the kids are school age, it's probably legal. If they aren't, she's breaking ratio laws and needs to be reported immediately. And her own children count into the ratio if they're there during operating hours. I would absolutely not use a daycare, home or otherwise, that broke ratio laws. And I absolutely would call state licensing and report a center that I toured that was out of ratio.
The laws where you live need to be consulted, but a person on their own can surely not be relied upon. What if a child is taken ill or has an accident - or if she does?!
Thats a high ratio for one person. Is she licensed by the state? If she is, you can check with the state any complaints that have been filed with her. In my state for a home day care, you can only have 6 kids for 1 person. After that they require you hire a worker for every x number of kids in the daycare. If these kids are school aged or some of them are, it's likely she just has them either before they go to school or after they get out of school. My youngest is only in school part time right now and her daycare provider takes her to school and picks her up from there. My husband and I are both already at work when she starts school and then still working when she gets out. They have multiple people who work there that transport kids as needed to/from school.