why did my turtle die?! :(

by melissa

i got a red eared slider 3 weeks ago. she appeared normal and healthy. then she got sick. i took her to the vet monday and he gave her a shot for vitamin A deficiency, said she was fine. then wednesday night i noticed she was breathing weird. it sounded like she was sneezing and gasping when she breathed. she also flailed her legs and then would stop for a couple minutes as if exhausted. when i woke up thursday morning she was dead. :(
why did she die???