need title, girl in mask with magic stone in bellybutton

a fantasy novel about a girl who is kidnapped by a witch and has a magic stone put in her belly button that keeps her from growing older. she has to wear a mask because the witch is jealous of her beauty and is kept as her slave. it also has a crow with a stone in his beak and some other animals with stones. Because of the magic stones the girl can talk to the animals, but when it is removed she can no longer do this. She is also saved from rape by unicorn who comes with her through journey but once stone is removed she starts to grow up and starts her period and the unicorn can no longer be touched by her because she is no longer pure. this is all I can remember. it has been more than 10 years since I read it so it is an older book and was not new then.

thanks for the help in advance this has been driving me nuts for months.

This is The Unlikely Ones by Mary Brown.

Aha! Magic stone in the bellybutton stops the aging process.

So noted!

More callous discrimination against outies.