Something Unique and out of the Ordinary that you know she would like.
http://www.teleflora.com/floral-gift-guide/birthday-gift-ideas.asp has birthday specific gifts. I am sure you could find something you like for your mom on there! :)
A car.
It really depends on what your girlfriend likes. Earrings? Music?
Make her a card, and show her love.
Since it's your girlfriend, you could send her one dozen long stem roses. This gift would be a romantic, thoughtful floral gift for her.
If you want a unique gift for your girlfriends 21st birthday, you can go to www.ugiftideas.com/girlfriend. This offers around 100 ideas to choose from, so you will most likely find the perfect one of a kind memorable gift.
Unless your girlfriend is an adult and/or your fiance, this sort of gift may be too "personal" a gift for you to give her. Her parents my consider this inappropriate.
I would suggest searching in department stores for ideas first. The kind of gifts I would look for would include jewelry, perfumes, cosmetics, even a digital music player.
Silver baby cup with the babies name on it.
Suggest that she buy them as a gift for your birthday or for a holiday that's coming up.
a gift card for a cheep pedicure........
Valentine day, birthday, christmas, anniversery, when she is in the right mood (calm, happy)