S.F.
It sounds like she is not comfortable enough there to show her true self. Some kids warm up to new situations right away and others take longer and are not as comfortable away from mom and dad, even though she's been there for 7 months.
My youngest daughter started preschool this past fall. At home she is very talkative and social. At school she is happy, but very quiet and doesn't interact with many kids, mainly playing on her own. My first child was the same way when she started preschool. But when she started her 2nd year of preschool she was much more social and outgoing and had lots of friends. I can see this will be the case with my younger child as well.
Some kids are developmentally more social earlier and some later. Is she in a large daycare with lots of kids? Maybe it is overwhelming for her to be around so many kids and she would do better in a smaller setting with just a few kids.