My first suggestion is to find a baby sitter for the younger two And go to school and watch your daughter through the window. For this tattling and what ever other issues you might be having with the school.
As for the tattling,You don't want your sweet daughter spending her whole morning at preschool watching the other kids and not participating in what she should be doing, do you? You want her to play and have fun. To do the art projects and listen to stories. Her Teachers job is to keep everyone safe, and she has to trust that they will do that.
The teachers have lots of other little bodies to be taking care of and if they have to be interupted by your daughter every two minutes because a is picking her nose and b just put the blocks back on the top shelf instead of the bottom shelf, Then it will be taking away from the time and energy they have to actually TEACH.
Now the flip side to this is that maybe A and B have problems and maybe they have autism, or some sort of behavioral issue and the teachers are dealing with the big ticket items with them like not hitting or biting, so they let the little things like ripping up the snack napkin or taking off their shoes slide because they need to not be harrassing the kid over every little thing. You can encourage your daughter to be a good example for a and b and help her to try to ignore those behaviors, OR you could always complain and try to get those kids kicked out.
If my kid was tattling ALOT, I would want to know. In every aspect of my kids education i want to be involved and let the teachers know where these behaviors are coming from, i.e. ''I probably encourage that at home since she helps me to monitor my other chilren.'' AND to work with them to make my daughters experience the best it can be. So if that means, I ask the teacher ''how they address the issue with her at school so that i can be consistent at home'', then so be it. If the teacher's rule is please tell me if someone is in danger, then at home-- tell her that the teachers rule is to only tell if someone is in danger, such as standing on a table, choking, bleeding, cutting something with scissors that isn't paper, leaving the room unattended, plugging up the toilet etc.
not being mean here, but been there done that, You may come to regret this behavior at home in another year or two when your little ones are big enough to start getting into the game and everyone is tearing down everyone else, You'll be spending alot of your precious time dealing with he saids and she saids.