Cecile: Gates of Gold by Mary Casanova
Twelve year old Cecile Revel lives in France with her father. While in the woods one day, she comes across a woman from the king's court who has fallen off her horse during the hunting party. Cecile brings help for the woman, and in return, she is rewarded with life in the palace.
Taking care of Madam's dogs seems like an easy job to Cecile, but when she learns of all the rules she is expected to follow, and also hears rumors about her father's previous life, living in the palace doesn't seem the same as she expected it to be.