Yes, she does have her own perfume. It is unlikely that the proceeds go to help amputees. The only woman she knew who was an amputee was Heather Mills. Whom of which she made it very clear that she dislikes.
I think Stella McCartney do not have her own perfume, but for sure she have perfume which she really likes, and there should be any information about it on her blog or own site.
