Usually in cases where the diarrhea is very short lasting as in your kitty's case, it's almost always from something they ate that disagreed with them or a little virus that caused it.
If it comes back or continues to keep happening, you need to contact your vet. They will take a stool sample to find out what is causing the problem and put her on medication (in most instances) to fix the problem.
Please let me know if I can assist further
Feline Healthcare
16 yrs health care mgmt & issues relating to cats, reproductive issues and multicat environments