The Girl Who Speaks Bear by Sophie Anderson
From Scholastic Press:
They call me Yanka the Bear. Not because of where I was found. Only a few people know about that. They call me Yanka the Bear because I am so big and strong.
Discovered in a bear cave as a baby, 12-year-old Yanka dreams of knowing who she really is. Although Yanka is happy at home with her loving foster mother, she feels out of place in the village where the other children mock her for her unusual size and strength.
But deep in the forest there are many dangers and Yanka discovers that even the most fantastic stories she grew up hearing are true. And just as she draws close to discovering who she really is, something terrifying happens that could trap her in the forest . . . forever.
So when Yanka wakes up one morning to find her legs have become bear legs, she knows she has no choice but to leave her village. She has to find somewhere she truly belongs, so she ventures into the Snow Forest with her pet weasel, Mousetrap, in search of the truth about her past.