ok, my brother is deaf and has a cochlear implant so hopefully i can shed some light on this situation...
First off, she speaks FAR FAR too well to have been entirely deaf before receiving the implant. My brother received a cochlear implant at the age of 18 months (he is 21) and his speech is about on par, maybe a bit better than hers, thats almost 20 years of having had an implant. (people ask him if he is a foreign student before they realize he is deaf, haha)
Over the years he has received several upgrades in technology which have allowed him to hear exponentially better with each upgrade. THIS is what i'm assuming this girl got. He described it as life changing, like going from listening to robots to listening to actual people. being able to hear minute differences in tone, pitches he could never hear before. I could see how such an upgrade would bring on a surge of emotions, obviously my brother was pumped in a not bawl your eyes out sort of way, but it makes sense that she would.
sparknotes: impossible for this girl to hear sound for the first time and process it and speak fluently. VERY possible that she received a life changing upgrade to the range of sounds she can hear.