hey, Steven Forth, glad you asked.  

Yes, she has a right to remix a Disney song, and pay the song`s copyright owners a royalty for doing so.  Happens all the time.  One quick example:  the British integrated reggae group UB40 had a good time--and a really big no 1 hit with an album track from white American writer-singer, Neil Diamond.  They had every right to record his song, Red Red Wine, and do what they wanted with it--in this case, completely change the style. Diamond was delighted (artistically, I suspect) but also because--he got royalties.