What are you feeding her?

Awwww! I hope she gets better.

Take her to the vet. It could be her food (I had one with a sensitive gut), something that she ate (do you let her outside?), bacterial infection, etc. DON'T wait to go to the vet. If she needs antibiotics, waiting makes things worse. My cat eats Iams dry food, which is very healthy, and was recommended by a vet when she was tiny.

Milk?

Take her now. Kittens are incredibly fragile and that could be a sign of multiple things.

Have you tried a higher quality of food with a larger percentage of crude protien? Of course making sure she doesn't touch foods like dairy is good too. All of my animals that I've had over the years tend to have bouts of intestinal issues when I switch food too quickly so I generally phase them into the new stuff. For the price and quality I recommend Costco brand Natures Domain, if you can find it. Otherwise I've had good luck with higher tier Nutro.

I agree with @Jnei. Kittens are like babies and can get th "Squirts" for no reason at all. If it is on going the Vet is the best recourse. Otherwise, watch what she eeats and make sure this is not a daily experience.

I know some one (who if you can stomach it) feeds pinkies (baby rats or mice) or chicks to her kitten / cats (from frozen defrosted) .. it takes longer to digest and works better .. I know that can help ! I would try a search online too.

It sounds like she's probably fine as she's eating and drinking - kittens do seem to get diarrhoea for no obvious reason from time to time, just like human children do. I'd still take her to the vet just to be certain, though.