Are these names too similar?

[casualreader2022]

We like the name Elizabeth.
Immediate family have an Eliza.

Too similar ?

Which nickname are you choosing? Libby? Beth?
Are they cousins?
Have you asked the parents what they think?

Thing is a cousin they'll see weekly who's six months older is totally different to a grandparent or an aunt or even an older cousin who they'll see at weddings and funerals. It really does depend on who and what the nn is

Just use Elizabeth, it's no big deal.