What it sounds like you are describing is colitis or inflammation of the large bowel. The signs can be very intermittent and can vary in severity, from normal stools to mushy to very soft, all even within one day at times. Passing mucus or blood from the rectum can also occur in some cases. There can be a sense of urgency to move their bowels and many of the pets will strain when having a BM, which to the owner can almost look like they are constipated. Many pets with colitis have GI discomfort and some will even vomit.
Colitis can have many causes including intestinal parasites, dietary indiscretion, food allergies or intolerances, metabolic disturbances from internal organ malfunctions, viruses, toxins, cancer or even stress. All cases should have a thorough physical exam to help rule out the causes mentioned and to make sure nothing more serious is going on. In her case, since she is acting lethargic, I would try to have her evaluated sooner than later. Intestinal worms, if present will not be visible to the naked eye and a fecal exam is to evaluate the stool microscopically for parasite eggs Intestinal parasites are one of the most common causes, but a rectal exam should be performed as well to evaluate the anal glands or to detect any other possible anatomic abnormalities.
Until you can get in contact with your vet, I would fast her to give her GI system a rest. Since he is an adult, a 12-24 hr fast will not hurt her and will let her gut calm down. Continue to offer small amounts of water at a time. When you do begin feeding her again, you will want to offer frequent, small meals of something very digestible for her. These would include items like boiled hamburger or chicken and rice or pasta. No sauces or gravies, but a little non greasy broth would be OK. If the stools improve, I would continue that for a few days and then slowly wean her back onto her normal food and feeding schedule.
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.