I think it's a lovely idea and your friend is lucky to habe such wonderful friends.
I just wonder if it might be an idea to give her a voucher so that she can choose the bag herself, unless you know her style and tastes extremely well. A bag is something so personal in terms of taste, how and for what purpose it is needed/used, that I would hesitate to choose a bag for someone else, because I would be worried that she might have preferred another one - regardless of how beautiful the bag I'd chosen was.