I C & P'd my response to someone else who previously asked the same question. Here's what I wrote
My DS started daycare at 15 months. Up to that point, he had a nanny. I won't say it was easy right away- it took a few weeks for ds to let me leave without crying. But the minute I left, he'd stop crying so I knew it was just to make me feel guilty!
Despite those few weeks where he cried, it was the best thing I did for him. He learned how to be much more social, he started eating more and talking more. He learned SO much that a nanny with one on one time could never give him. Kids learn more from their peers than from anyone else. He is great at sharing toys, learned how to make friends, etc. Kids relating to other kids is very different than relating to a nanny and I immediately saw a good difference in ds.
What advice do I have? Stick with it. Don't get frustrated if your dd has a rough beginning. My daycare was great (in comforting me!). They constantly told me it was normal and ds would adapt. I wasn't so sure and really wondered if I did the right thing at first. But then - poof- one day he went into daycare and ran to his friends without even saying goodbye to me. End of crying. Now he runs TO daycare and can't wait to get in the stroller to go in the morning. He sometimes cries when I try to take him home at night because he likes it so much. So stick with it. Your dd will be happy in the end.
Also, don't worry about the one on one time. Obviously, each daycare is different but I found that even with a 3 to 1 teacher to student ratio, they get a lot of attention. Sometimes the kids are just needy or sometimes they're teething or whatever. The teachers know when a kid needs extra attention and they get it.
The one thing I was not prepared for was illness. DS was never sick before daycare and in the first few weeks, he had 2 colds and pink eye. He hasn't gotten sick since those first few weeks and everyone told me it's normal for kids to get sick when they first start daycare because of the additonal germs. So I'd make sure you have some sick time saved up and are prepared to take days off if your dd gets sick.