My daughter has an iPhone 4 (AT&T) and the battery will no longer hold a charge. Her contract isn't up until July and, being a full time student, she can't afford a new phone right now. Any ideas on how to resolve this issue?
You will likely need to replace the battery. Many websites offer professional battery replacement services, you can even usually find places at the mall that do watch repair that can replace the battery for a fair fee. This is the nature of the batteries that're used within iPhones, they are designed to slowly hold less charge over time, especially with partial charging. The only other thing you can do is try a factory reset on the device, as there may be an application installed that is draining the battery quickly.
An even cheaper but less warranty friendly solution is to just do it yourself. It's a simple procedure unlike most iphone repairs and should take only 5-10 minutes and cost less than $10 USD.
Buy one of the most top rated iphone batteries off of a reliable website such as Amazon. Make sure to buy it from a seller in your country or else you will wait too long for the battery because of shipping time. Buy a cheap ($1-$3 USD) iphone toolset as well. Take the strange looking "pentalobe" screwdriver and remove the two screws at the bottom of the phone. Slide off (upwards) the back of the phone. You'll see the battery and it will be held down by one screw. Remove the screw, remove the battery, and reassemble it, making sure to put all the screws back.
I'll provide links to a good battery and a good guide when I'm on a proper computer.
If you don't want to do that and don't mind sacrificing your daughter's smartphone access, buy a cheap go phone from a local store such as best buy or walmart. Then go to your local at&t store and ask for a normal sim card so that your daughter can use the go phone with her phone plan. They'll happily give you one.