So Sorry for your sudden loss, I just had one pass yesterday that was also sudden fine one minute and gone the next. As for what happened its hard to say without having a Necropsy done by your vet. Again I'm so sorry and your in our prayers.:(
You were with us such a short 2yrs and you left us so sudden, I wish you could of told us what was wrong. Fine one day and gone the next .:( You touched our hearts and souls with your sweet/quirky way and will be forever missed.:(
So sorry for your loss. I know your feeling having just lost one recently also just hang in there and try not to let this discourage you from the hobby. Just Know your little girl is in a better place and feels no more pain.