Hi M.,
I'm a home child care provider myself. And this is how I deal with the tantrums starting at at about 1 and up.
If a child whether it be mine or a daycare kid wants to throw a fit for one reason or another, they can but they have to go to the corner in another room. They are sent to the dining room, in the corner to "have it out with themselves" when they are done they can come out. The child can throw a fit all they want to but they are not going to do it in the presence of me or the other daycare kids. I don't believe in the term "it shall pass" or "ignore it". I can't ignore a child screaming child in the middle of the floor because they didn't get a certain kind of juice they wanted or snack. They can have what I gave them or do without. In my house the can get happy in the same pants that they got mad in.
If your daughter was in my care and if she started throwing a fit for whatever reason she would be sent to the corner until she could calmly tell me what she needed or wanted. Then if she still didn't like my answer and still wanted to throw a fit she would be sent right back. That is the one thing I don't tolerate out of my kids including daycare kids. If they can talk then they can use their words.
For you, you have to be consistent on whatever you decide, if she starts to throw a fit you have to do something about it right then and there, even if you have to pause what you are doing with the group to send her to the corner. After a couple of times of her throwing a fit and missing out on things she will get the hint that throwing a fit isn't such a good idea.
This is just my opinion and what I have found to work with the kids I have watched in the past and currently. W.
I have a 1 year old that if I put him in the corner for not being nice to other kids he will sit there.
I do have a question though, when one of your daycare kids "throws a fit" what do you do ??