The XN-- domains means they contain an unicode character, emojies are unicode, so technologically nothing can stop you.
Your .🍕 would look like this in that list: xn--vi8h The price of a new tld is USD 185000
More importantly, she actually put out better songs on her own later on with much less manipulation. Its not at all my taste of music, but I acknowledge her actual talent for singing:
https://www.youtube.com/watch?v=cxZ_fIAJZpw