I'd be inclined to tackle a small club management system because she could start with a simple Address Book and build other modules from there. I'm in several small clubs and a simple system with add-on modules doesn't exist. The only thing I could find was "TidyHQ" which is web based and costs money.
The basic or core module could be the Membership List. That in itself can use a Relational Database. Three items are essential:
1. A decent search facility
2. Reports in various formats
3. Bulk Emailing
I designed a similar Club Management system using Appgini.
Unfortunately Appgini doesn't do reports or bulk emails. Also the search facility could be better.
I then added modules, the most important being an Inventory and that's another great stand-alone PHP project you could design.
Another module was fund raising. Where did the activity take place, the members involved, the hours they worked and the cost/income.
My reason for suggesting this kind of project is because Blogs and Photo editors are a dime a dozen. If I was about to design something, I'd look at the potential market and look outside the square. There is a need for a small club management system and if it's good enough your daughter could sell it for a few dollars.