Well, more than a simple "yes"..........
If she is running a 3, any upgrade will be stunning!
4 is a very real option and cheap, but.....
Go to a 4s.....minimum. The 16gig are about $50 with a contract.
The performance of the 4s doesn't lag much behind the 5.
Yes, the 5 has a faster processor and better face time camera but beyond that????
Truth be told, the 4s has a really fast processor, the 5 has a really really gas processor.
You will see an amazing difference from your 3 to a 4s!
On the other hand the performance difference between the 4s and 5 won't be so noticeable.
I've two 4 and two 4s units in the home. I see no reason to go to a 5 from my 4s units.
Honestly, I'm waiting for the 5s (or whatever they will call it) to come out. At that time I may move up to a 5 when the price drops $100 or if the upgrade is truly compelling, jump into the "5s".
In conclusion........ 4S minimum.
Dave