What do i do when my dog attacks my cat?

she growled a little before but then she just freaked out and grabbed the cat in her mouth and started shaking her by her back left leg. she has a small bit on her hip but the inner part is very raw and she wont put any presure on the leg. she ate a little wont drink any water and i dont know what to do about my dog. we have a small mini weenie puppy and in scared she may try and hurt her mext. she doesnt have any history of attacking anything but bugs. shes always loved cats and she likes to play with the new puppy. im very worried she may hurt her, bt i DO NOT want to put her down shes only 5 and the first dog ive ever had. what do i do??