I would choose
Estelle. I like that it's shorter.
Alexandria is pretty, but it seems like a bit too much, and my friend
Alexandria was just another
Alex when it came to school time so the name didn't really stand out.
Estelle is rather uncommon, but it's not a difficult name and I've always been a fan of -elle names. It is somewhat difficult to make a combo for though.
Estelle ConcordiaEstelle FrancesEstelle JessamineEstelle MagnoliaEstelle MercyEstelle PilarEstelle RosalindEstelle ValerieEstelle WillemijnEstelle Flannery