I don’t think you are being unreasonable to want your daughter to be called by the name you chose for her. I hope she has a say though!
I’d never dream of shortening anyone’s name unless they told me that they commonly went by, say, Em instead of Emily or Dave instead of David.
I’ve got a lovely name which people insist on shortening, usually people men and the occasional lesbian I barely know and who are trying to be overfamiliar get in my pants.
I hate the common shortening of my name as it’s a word that describes something not very pleasant. Think “Tash” for “Natasha” or “Tit” for “Titania”. I say, “Sorry but I really hate being called Tash, please could you call me by name, Natasha?” (but obviously my name isn’t Natasha). Then quite often they get all huffy and offended, no matter how nice and polite I’ve been about it.
I’ve got family members who’ve known for years that I hate it but who continue to do it and have now taught their kids to do the same.
I don’t understand the need to shorten names at all and I’ve often heard shortenings where I’ve thought, “Really? Listen to what you are saying ffs!”...like Nads for Nadia and Nadine, Kirst (Cursed?!) for Kirstin, Cyn/Sin for Cynthia. And the poor owner of the name just sort of smiles weakly like they are well and truly sick of being called by these ugly “pet names” but know they can’t say anything for wont of being accused of being uptight or stuck up.