What is the song "NOTHING COMPARES 2 U" really about?

A friend and I had an arguement the other day about the content of the song. I believe it is about a boyfriend who has broken up, my friend claims it is about the loss of a mother..

Anyone who have an answer?

"I could put my arms around every boy I see
But they'd only remind me of you"

that would imply it's about a boyfriend indeed

"All the flowers that u planted, mama
In the back yard
All died when u went away"

and this with the mother...

Maybe the song is about both... and anyway you should interpret it the way you see it...
I know that Prince wrote the song for Sinéad, but I don't think that that will give us more clues as to how to interpret the song

Seeking Google for "Prince - nothing compares 2 U" give the lyrics "And all the flowers that you planted SUGAR <-- and not mama.. Maybe that is and indication of something?!

that could very well be... maybe O'Connor's mother died before she released that song, that's possible... but what does she sing? mama or sugar?

She sings "mama" but I don't know if her mother is death??!

me neither

when she sheads a tear in the video it was because the line reminded her of her dead mother.