guess the hand

So, who's the lucky lady with this huge ring on her finger?
Well, she ain't only lucky! She's young, beautiful and married to one of the most powerful men in Hollywood. Her acting career is fine, although her last movie didn't bring in so much cash at the box office!
She's also a mom to a tiny, cute daughter!
Did you guess who she is?

Update:
Six of you got it right!
This is Katie Holmes' hand and ring! That's a big rock right there!