I'm willing to go on record as the dunce who might not realize that Elizabeta and Elisa are related names, or that they're the same person. Same for Mia and Miranda. It's going to take serious context for me to get it and remember it.
In my world, Elisa is its own name, not a diminutive. Same with Mia. If that's not the case in your world, and you're certain your readers will be in your world and therefore know exactly who you're talking about, then all is well. (I'd have no problem with Elizabeth and Liz, Judith and Judy, or Margaret and Maggie, for instance.)
Surely I can't be the only reader who's become confused when a single character goes by Bob, Robert Lee Smith, Sheriff Smith, Bobby Lee, R.L., and Bobo. More than once, I've realized rather late that what I thought were two characters was actually one, and I stopped reading in disgust with both myself and the author.
Maryn, who, like many readers, cannot always devote long stretches of her undivided attention to reading