My red eared slider was in salt water for 30 minutes and now i think its dying help?

i just got a red eared slider and hes a couple inches long about as big as my hand. he came to me with a little fungal infection so i looked it up online to find a good way is a warm salt bath for half an hour so i did that. right away i knew something was wrong she was frantic (probable because of the small tank used to clean her but then i relized i think i used waaaaay to much salt 13cups of water 1/4th cup of salt she was wheezzing then sank to the bottom a wasnt moving after the time was up i put her back in her tank hopping she would swimm and be happy but she sank to the bottom OMG IS SHE Dead!