hi hermom
Carolyn has given you some good links there, although, as she mentioned, the Latitudes forum had a pretty bad crash and so is currently only showing a read database..........still there is a ton of information there on PANDAS as well as many other aspects of TS and tic disorders
It really would be worthwhile IMO to have strep blood titres tested in order to check for possible PANDAS, especially with your daughter's history of scarlet fever and strep
here is what the NIMH says re PANDAS/scarlet fever/strep
http://intramural.nimh.nih.gov/pdn/web.htm
The only reason to avoid dairy would be if your daughter is found to be lactose intolerant or with allergy/sensitivity to dairy products...otherwise they are fine as is any other natural food group.
Artificial food additives however really are best avoided as they have a well documented trigger effect on tics
hope that helps a bit