Hi Cindy,
Your sister’s Furby is most likely fixable! Depending on what the problem is, you may need to disassemble it.
But before you do,
* Check if the battery contacts are clean and not corroded.
* If there’s a reset button on the bottom base, press it to see if that will work.
* See if the Kirby is improperly parked…[https://www.instructables.com/id/Push-Start-a-Comatose-Furby/|check this link].
[[Topic:Hasbro furby 2012|Here are some guides]] to help you take it apart. If you do disassemble it, look for loose wiring, especially ones that come out of the battery pack. Good luck with your repairs!