Once the child has truly expressed a thoughtful preference on their name, that is their name. Personally, I wish no one would ever call me by my name anymore. It's not my name. It doesn't fit me at all, in any way. The nicknames don't fit, and I wish I could change it, but I feel like it's too late.
But a kid's personal identity is not their parent's decision to make. Like, a parent can decide that they don't want a kid being called by a silly nickname - if the kid introduces themselves as 'Princess Ju-Ju Bee' and the parent says "Her name is Elizabeth", then I don't see that as the parent being controlling. But if little Elizabeth introduces herself as Lizzie, Beth, Bess, Betty, Liza, Liz, or Eliza... or by her middle name, then I don't think it matters if she's 5, 15, or 25. She knows who she identifies as, and as someone who struggles with name identity, I respect that more than I respect the parent's desire to have her called what they wanted.