As a general rule, I would suggest a home replacement app like ADW or Go Launcher as a first try at fixing it. It removes a lot of the "skin" and lets the phone run better. Get rid of a task launcher if she has one, they cause more trouble than they fix.
If it was my phone, I'd root it and go searching for a nice clean, minimalist ROM and kernel to cut down on the bloat and wasted cpu cycles, but that's a whole order of magnitude above a home replacement app and involves voiding your warranty, etc, so I try not to suggest it too strongly to anyone who feels unsure.