Technically, I don't think it even rhymes, it has the similar 'va' sound, but not the AY sound that is in
Ava.
Caoimhe is still completely okay to use with
Ava. I mean think of how many sisters and cousins out there from our generation that are called
Kelly and
Katie, or
Kaleigh and
Riley now. It will be fine (and
Caoimhe is a much better name, imo, than the ones listed above.)