I am a curvy girl and the Diorama in medium (I have two) suits me well - but then I do like smaller bags. I also carry a chanel WOC - I think it doesn't matter on your body size it is how you style things. I also have big boobs - can wear the Dior cross body but I personally prefer this bag on the shoulder. I am so jelly of your sister getting one of these - she will love it. As far as colour transfer - well you do have to be careful with any lighter bag especially if the person wears denim. Hope this helps.
Thank you! That is very helpful!