Just don't EVER use the name 'Marie' - it is the most common possible middle name and it means BITTER - how horrible is that?!
Growing up an A. Marie (a VERY common name in my generation, to be sure...) I hated my name and I always wondered why my mother had given me it. It turns out that she had her own reasons so I don't hold it against her anymore, but I am still not fond of my given name.
So, I guess it pays to really know what the meanings behind the names you give to your children are.
On the account of sound, I like the name you picked out and I've always been very fond of Gabrielle. I think they sound and look very well together.
Her first name would mean either "Black" or "Lady" depending upon the source language you would be taking it from. And then, of course "God is my strength" is the meaning of her middle name.