I like it better as a fn, but I think that's because it ends in a -y (and most -y names sound better as fn's to me, but that's just me probably :b). But the combos you suggested actually all sound lovely together and the flow is quite nice.
My favorites are
Claudia Ruby,
Lucinda Ruby,
Susannah Ruby, and
Sylvia Ruby. I also like
Agatha, though. The only one I don't care for is
Twila, but it's not awful by any means. :)