Yes I also believe a small child misses their mom especially if they are away from them many hours a day .part time work for mom seems to be best if a family can do it ...
She's a preschooler. My guess is, she needs her mother.
From time immemorial, kids have started school at 5 or 6. Until that time, they were with their mums. I believe there's a reason children were with their mothers until that time - because society recognized they needed their mommies.
The first type of action I would advise is to ask questions. Lots of them. I would also observe very carefully to see how the other children are behaving and in particular, playing. How does everyone communicate with each other? Do the staff members do any yelling or show any signs of impatience? Do any of the children seem afraid of anyone? What is usually going on when you drop off your daughter? Are games or educational kinds of activities taking place? Do the other kids seem bored? Pre-school children are normally inquisitive, easy to interest, enthusiastic, and a joy to be around. Keep an open mind and don't start accusing the workers of anything unless you're sure there's a problem. If they think that you are suspicious, you'll be unable to find out anything at all. But, DO keep your eyes and ears open. Talk to your daughter at home. Ask her pointed questions concerning what she does or does not like at day-care. Be positive and show a lot of interest in what she has to say--no matter how trivial it may seem. Best wishes. Hope you find some answers.
Possible boredom , do they play with them how do you mean 'she sits there' ask the daycare what stimulation the children are getting, if they are bored they will tune out ..good luck