I worked in a number of nurseries and visited many more as a prospective employee.
If it’s not essential to send her, keep her home.
Yes, children come in happily, but that does not mean it is the best for them. They accept most things as they have no other choice.
At this age they have no ability to ‘socialise’. They play near to other children by default due to the set up.
Staff turn over is generally high, the children aren’t given the love they would do at home, although their needs are met and the staff mostly tend to care about them (on the whole). Sadly not always, in my experience.
Times such as going outside, coming in, preparing for meals, eating etc are all rushed, noisy and chaotic and the quieter ones can really struggle. At this age, children are totally focused inwards on themselves and a more timid child can be swept along without having the time to sit, assess, feel confident.
Nursery can be beneficial to older children, but not at this age. They need a nurturing, constant adult presence, time to quietly just ‘be’ and take things in and time to explore and make sense of their surroundings.