Toddler walks at home but not in nursery

Our 15 month old is a pretty happy child, she is super active, walks a ton at home, non stop really. However at day care they tell she never ever walks. They say she's potentially intimidated by other kids, and that sometimes she does move a bit more at the end of the day when other kids have already left. We're moving her to a another day care in a couple months, where kids are slightly older, so the intimidation might get even worse. We don't know how to fix this! She's just shy in public I guess (not with us).