I say:
Ava, AH-vah
Eva, AY-vah (AY like ape)
Iva, EE-vah, but that's knowing its origin. I might be tempted to go with EYE-vah otherwise since it's so visually similar to
Ivy EYE-vee.
I very seriously dislike
Eva said EE-va. I'm from the US, as a matter of interest.