I think Rosalind is pretty & Luna is a perfectly fine name/nickname. I expect when it comes time for school/drivers license/passports/filling out forms, she may just put Rosalind Altalune as her first & middle names. That way Luna wouldn't be confusing as a nickname.
I'm not sure official forms expect all the names. Most just ask First Middle Last. I expect Rosalind Altalune would be legally acceptable.
Either that or she'd need extra forms.
The multiple names may be overkill, but I don't find them nearly as bad as oddball names. You know the ones I mean. Those are the ones who's parents are trying too hard to make their kids seem unique.
Kind of like those self important mothers who act like they are the first women to ever carry a baby & everything is oh too precious & total wonderment.