Definitely too similar for sisters, but they're both good on their own.
I don't really like
Eve "eev" (too short) or
Eva "eev-a", but I love
Eva "eh-va" or "ay-va", and I really love
Ivy. If your name is
Ivy, people will probably just think of the plant and maybe some fictional characters, not a medical IV. I don't think poison ivy is a big deal.