I usually dont post on sajha but seeing so many people taking sides I wanted to put my 2 cents. Personally, I've lived in US for over 8 years and have never heard of her or any of her songs. I might have heard her song in some of the Nepali parties I attended over the years but hadn't been aware off. So, getting to the point, I think as a person she has every right to sing or not sing any song. Whether it's a hindu bhajan, or praise allah or jesus. But as someone point before me that artist is not limited to any boundaries and I understand where that person is coming from. As a Nepali, I listen to English, latino, Chinese as well as Korean song ( am sure many of you have heard Gangnam Style). Anyways, since she is a celebrity, she should've chose her words more carefully. She should've just said I don't want to sing a song that would've been the end of it as am sure many artist have refused to sing a song or act in a movie.
But to say my religion wont allow is totally wrong. Just because you have freedom of speech doesn't mean you should be allow to speak anything that might cause hatred among other people. For instance several months ago famous TV Chef Paula Deen used N* word and caused major controversies which caused her to lose many sponsors and even lost her TV contract. Same was the case when Duck Dynasty dude spoke hatred about gay. I hope you guys know where I am going it this.

Tl:Dr: Just because you have freedom of speech doesn't mean you can offend other group of people and hope your freedom of speech covers the statement.
-LB