I remember being pregnant and situations like this meant more then than they do now. Ultimately, it is really no big deal (I am not saying you are making a big deal about it!) I think connecting with her would be good, making it a light conversation, with humor, honoring your friendship and acknowledging you are not surprised you like the same name, noting other things in your lives you have in common, I am sure there are many.
There are totally worse things in life than having the same name as a playmate, however, it does not feel that way when you are pregnant and beside the health of the baby, the biggest thing you concentrate on is choosing a name.
Other posts are right, it may even be a mute point, her baby could be a boy. And, she has many months to go, names come and go, she may not even feel the same way about it when baby is born.
It is not worth weakening a friendship over. Join together during this precious time of life. Have fun together! You may never be pregnant again at the same time!!
Also, info for both of you: If you are looking for a birthing method, check out the classes I teach for HypnoBirthing. www.YourPeacefulBirthing.com
Good luck with everything,
J.