Hi, I'm Dr. Deb and I'll do by best to assist you today.
I'm sorry for this concern for Susan but looser stools in a kitten this age is not all that uncommon.
The most common cause of loose stools in a kitten this age is going to be internal parasites such as round worms. Other parasites such as coccidia, giardia, and hook worms are possible, too, but rounds worms are by far the most common.
The treatment for round worms would be pyrantal paomate which is available at many grain and feed stores. It is a very safe wormer and is very effective. I advise treatment every two weeks for three treatments. All cats in the household should be treated at the same time so they don't pass these worms back and forth.
These worms often cause looser stools although they don't usually cause blood. Is she were straining a bit to defecate, though, a small amount of blood might be produced.
Another possible explanation for blood would be coccidia. This parasite is the most common cause of blood in a kitten's stool. Albon is the treatment of choice but would need to be dispensed by a vet.
This LINK discusses this problem in some detail.
Even though stool samples might be negative, parasites could still be the problem. Eggs are not shed in every stool sample that we examine. A positive is a positive, but a negative does not mean a negative, if that makes sense.
I wouldn't get too worried about Susan at this point. If the stools become really loose or contain a large amount of blood, then I might have her seen or discuss the situation with the owners. But more than likely, she will need to be wormed at some point; otherwise her stools will continue to be loose.
I hope this helps.