I am sorry to hear about this problem with Cleo. My name is Rebecca. I am a veterinarian and will do my best to help.
Is Cleo the only cat in the house?
How many litter pans do you have?
Is her stool dry and hard at all? The blood bothers me; if her stools are excessively hard, and defecating is difficult or painful, that could cause the blood and also be the reason for her not using the litter box to defecate. If her stool is hard at all, you could increase the Miralax; the usual cat dose is 1/4th teaspoon twice daily.
Adding canned unsweetened pumpkin or cooked sweet potato to her food may also help.
These are the things I try when it is a behavior problem to try to get a cat to use the litter box:
Get Cat Attract litter, or add Cat Attract (an herbal product) to the litter.
Add catnip to the litter.
Spray Feliway, or get a Feliway plug in unit to use near places she is urinating. It emits a pheromone only cats can smell that has a calming effect.
Have at least one more litter box than you have cats.
But I would still try to find out why the blood, and the odd behavior preceding her defecation. It sounds like there is inflammation or pain somewhere. Trying her on a course of pain medication from your veterinarian might be something to try; if she starts to use the box, then something is hurting somewhere.
Let me know what else I can help with or answer. Rebecca