Well, there is a good chance that the loose poop is caused by some sort of parasite and the only way to fix that is to take a stool sample to the vet and get medicine if necessary. However, you also need to be sure that you are feeding her a good quality food. What is she eating? She should be eating kitten formula food at 4 months old. Changing foods can cause a tummy upset and diarrhea so if you have been giving her a variety or trying different brands, please stop and limit it to one thing. And don't share your own food with her. Also, NO milk. Cats and Kittens can not digest cow's milk and that will cause diarrhea.
"One cat just leads to another" - Ernest Hemingway