Your little girl sounds like she's right on track. She'll talk when she's good and ready. My son didn't say more than a couple of words at 12 months and now, at 27 months, he's a great talker. She may be working on something else developmentally and taking a break from talking. That's ok. You don't have to force it. Every child will learn to talk in their own time.
I would be concerned about the sitter and the TV issue. Are you paying this sitter? If this is her profession, you have every right to challenge her use of tv to do her job. Sounds like she doesn't want to confront the inevitable conflicts that come with a house of 4 children. (it takes a lot of constant energy and patience, which personally I wouldn't want to do, but that is why I do not choose to be a professional day care provider) These conflicts however, are neccessary for the children to learn how to be considerate people. I would recommend looking around for another sitter before you talk to her to see what else is out there. Try to observe during the day for at least an hour. You will be able to see how they handle sharing, taking turns, etc among the children. She should be patient. The caregiver should not be yelling at all and raising their voices only rarely. She should not be trying to do housework with the kids there, other than folding clothes in the same room as the kids. There should be plenty of open-ended toys to play with like blocks, cars, dolls, babies, tinker toys, a doll house, kitchen stuff, legos (not the itty bitty ones. TV is ok for the older kids that don't nap during naptime, but movies are better since they have a longer story to be told.
I had a sitter for my daughter that I thought was great since she had the same "attachment parenting" philosophy as I do. She wore my baby in a sling and had other similarities to my own parenting style. But sometimes when I dropped off my daughter as she was able to walk, the sitter, would sometimes not come over to the door to greet my daughter with a hug. I found out when my daughter was about 18 months old, that she was not playing very much at the sitter's house and that she was totally uncomfortable there. Anyway, it was a good parting time because my son was about to be born, so we parted ways. I found another sitter that had two openings for my two kids four months later. By observing the new sitter, I found out how much the first sitter was lacking in her ability to communicate and engage my daughter. So the moral of my long-winded story is: if you feel a little uncomfortable with something at the sitter's house, you are justified. Just because you like the sitter personally doesn't mean that she is the best for your child. I felt horribly guilty for months afterward, but my daughter has recovered beautifully and is a very social 4-year old now.
Hope this helps. Sorry to be so verbose!
Laura