I would reregister through AVID, if they have the onetime fee program, since she already has the chip. I would not use a company that makes you reregister every year, that's so annoying. This site has a phone number, and will probably take credit cards, it also has a fax number you can use.
Avid Microchip Registration That way Uni will be registered with both companies! Anyway, why make Uni go through the pain of another chip implant?