Well, does she currently have service with verizon? The last time I renewed my plan was when I got my Razr V3m on my NE2 (new every two), and I had to agree to FURTHERING my contract, however, this is not to be confused with UPGRADING my contract to one of their newer nationwide plans.
Now buying her a phone off eBay is easy, and if she already has verizon, all she has to do is use the online
ESN switcher to change to the 'new' phone, then dial *228, chose option 1 and she's done. If she doesn't have verizon, then she might be able to do it over the phone, but may have to go to one of their stores.