I bought this one after owning one similar 15 years ago:
Canon Deluxe Backpack 200 EG 6229A003 B&H Photo Video
And it currently houses my K-x, the 100-500m I got from you, my kit lens 18-55mm, my two 50mms; well, about 6 lenses altogether. If she doesn't have as many lenses or longer lenses like I have, it should fit her nicely. It is very durable, and water resistant too. I love mine.
Oh and I forgot to mention the many pockets, and zippered compartments that carry all my gadgets, inside the first zippered pocket, it has two additional pockets for filters, or lens pen, or whatever she might want to put there, at the top of this pocket is four small pockets with velcro closures for SDHC cards. Total pockets, two small velcro closure pockets, I could take photos if you want? Let me just say, it has more pockets than I really need but I've filled them with all manner of photographic items.