You DO have the DTCs? Great we have been pleading for them! (Or were they some other first two sentences?)
That sucks. If you have DTCs (they're probably in the format Pxxxx)), that would help confirm. The only thing you could try is to see if the dealer (or a good dealer) can take it up w/Toyota to see if they're willing to cover some (or most) of the cost. You aren't that far outside the warranty. This particular amount of time and mileage for HV battery failure is a bit on the early side for a Gen 2.
RAL Bummer if there is any way to work it out I would keep her. A new traction battery in a Prius with those low miles and you likely will have good cheap transportation for another 100000 to 150000. If I was near enough and the car otherwise is in good shape I would trade you a fine F-250 gas guzzling work truck with 110000 miles on her. RAL