I think
Anastasia and
Rebecca work okay together, despite the former feeling, to me, more formal than the latter. I also like
Rebecca and
Lily together.
Anastasia and
Lily feel very different to me, so I would prefer
Lilia alongside, but I wouldn’t let the difference stop me if I really loved all three names. My only other impression of real difference, beside formal feel, is in temperature;
Rebecca and
Lily both strike me as warm, where
Anastasia feels winter-y, but that’s probably just me.