Lexy/Lexa. I've never been a huge fan of the Ally/Alex string of NNs.
As for a MN I would go with something a bit shorter because
Alexandria has so many syllables, but that still sounds a bit unexpected. Something like:
Alexandria TesniAlexandria MaudeAlexandria IvyAlexandria GaelleAlexandria VerityAlexandria Gable
Alexandria Forsythe
Alexandria ColetteAlexandria BrynAlexandria NoyaAlexandria BetteAlexandria AdiletAlexandria LisbethAlexandria Greer