That's a very sad story. Thank goodness this little girl has you mlle.c. Right now I have a 2 year old boy who came to me with his soother 24/7 in July and I weaned him off it immediately and the Dad talked the Mom into doing the same within a couple of months. This boy learned to talk with the soother in his mouth and now he can't form all the letters and I can't understand him half the time.
He's also very oral with toys and his fingers and I am a tyrant for saying 'out of your mouth' all day every day and he's getting a little better every week. I can't stand all that drool on his hands then he touches all the toys and it grosses me out completely. I mean, it's very unsanitary for people even to touch their faces! That's how we get germs, when they are close to your mouth and nose, gross!
Anyway, don't stress over it and just do what you can do while she is at daycare. You have to know your audience. Sometimes parents listen to us and sometimes we're hitting our heads on a brick wall. But it isn't your responsibility, you're not the Mom, so just do your best and call it a day.