My dog was attacked by another dog HELP !!!?

Ok i was walking my dogs to day (there Yorkshire Terrier mixes) and a Collie came and attacked my girl dog the collie picked her up from the back and shook her i tied to stop her but i couldn't until the owner stepped in he was 2 houses down now she has not been the same she has no external injury but if i touch her were the collie bite her she yelps and when no one was near her she jump up and yelped in pain she walks fine but i gave her a bone and she won't touch it she ate her favorite food carrots so my question is how to tell if she has internal injury's and how bad it is