Thanks for the additional information. I really appreciate it.
It sounds to me like this could be bloody urine rather than feces. And unfortunately, bleeding during urination can be caused by many things that range from the rather benign (like a urinary tract infection) to the more dangerous (such as bladder cancer). In addition, there are issues like bladder stones or kidney disease that can present with bloody urine.
Stones are caused by things such as minerals in the urine, bacteria, certain medications, an excess of Vitamin C in the diet or even their diet (which can affect the pH of the urine). Usually a course of antibiotics and a diet change to a prescription diet takes care of the problem.
Kidney disease can happen in any breed and unfortunately, at most any age. The contributing factors can include dehydration, cardiac issues, tumors, blood loss from traumas and both infections and ingestion of toxins. Even some medications can impair kidney function and lead to kidney disease. Generally this is treated with supportive care to keep the dog comfortable and to help improve kidney function.
Urinary tract infections (also known as UTIs) are the number one most common cause for bloody urine in cats. The infection can be located anywhere in the urinary tract from the bladder to the kidneys. Certain medications and underlying health problems such as diabetes or viral infections can also lead to UTIs. In cats, even stress can result in bloody urine and UTIs, and since Riley wasn't a giant fan of the puppy, it's definitely possible that's what set this off.
The important thing is to have your cat seen by a vet as soon as possible for evaluation of the blood in the urine. Bloody urine is never 'normal' and can get worse if left untreated. Your vet will likely want to run a urinalysis, so if you can catch urine from your cat before going (you can catch it up to 24 hours before your appointment, just keep it in a clean, closed container in your fridge. Do not leave it out of the fridge as that will cause bacteria to grow in the urine and may give you false positives). Hopefully it'll end up being nothing too severe, but early intervention is the key.
I do understand it's a holiday weekend, and most 'normal' vets aren't open until Tuesday, so you may want to look into having her seen at an emergency vet. You can go to: http://www.vetlocator.com and plug in your zip code. They'll point you in the direction of the one nearest to you.
If there is no emergency vet near you, then you can monitor her until your normal vet opens on Tuesday, but ideally, finding an emergency vet would be the best option.
I hope this helps