You should be looking for two things.
RAM space - the more you have, the more applications you can run at once. I imagine she'll be looking at a piece of software like Adobe Photoshop - this is something that you use to enhance your photos (Redeye reduction, adding layers to create more complex pictures that you can't take just with a camera etc.). Some Laptops might still have this as a free 60-day trial (Mine does, but it's about 5 years old).
Hard drive space - again, the bigger the Hard Drive space you have, the more photos you have the more you can store. Also, the amount of megapixels the camera uses will have an effect on the size of the file - I took one of my great-nephew with a 16 megapixel camera and the file is over 6mb in size.
You's probably be looking for a 15.6 inch screen size - a 17 inch screen laptop will be a little heavier, so portability might come into it as well. They should come with an HSMI cable, so it could be connected to a suitable TV - that might help too. Unless she really likes her music, don't go for the Hewlett Packard models with the Beats Audio package - they're a little bit more expensive.
Opinions on brands vary. My laptop is a Sony Vaio and (Touch wood) have ha dno problems with it. Might be worth having a trawl through the Computers sub-section and seeing what other people have written.
Hope this helps.