I don't believe there ever was a white Keira. I had one and it was darling but small. I doubt it could be a cross body bag as the strap is a shoulder bag but not terribly long. Unless maybe you are very very tiny.
I just got the Meredith today - the longer strap on that bag can definitely be worn across the body. The style of this bag is very siimilar to Miu Miu's Coffer bag - the longer shoulder strap on the Meredith is a lot like the strap on the Coffer bag
I've had 2 Keira's, no way can you wear it cross-body, the strap is too short. I'm thinking the strap drop is about 11" or 12", so unless you're really, tiny it's not going to work!
The Annie has a real similar look to Keira, but with a cross-body length strap. It's a larger bag, but will give you the same look with a longer strap. Check the threads, there's pictures, here's one: http://forum.purseblog.com/kooba/pictures-of-your-koobas-120816-9.html#post2901395