Helena at least has similar letters.
Persephone doesn't.
I know you can pronounce
Helena hel-LAY-nuh (how i pronounce it). I think you could get the nn Lainie no matter how you say it though. I don't think it's confusing at all. And there would be no reason for you to constantly explain it to people unless she introduced herself as, "Hi, I'm
Helena but you can call me Lainie" and the other person was dumb enough to get confused by something so straightforward.