(I emailed you off list...did you get it?)
In my experience, a chameleon doesn't just pee or pass urates without passing feces unless there is a reason.
What color is the blood? Red? Black? Orangey-brown?
You said she passes some feces so she can't have a complete blockage obviously...but she could have something stuck inside her. Is there anything that she could have ingested that could be stuck in her? Soil? Plastic plants? What does the feces look like when she does pass it? It should be soft and moist but not runny and look like a small sausage in a casing.
Sometimes parasites can cause some blood to be passed....but I'm not sure what color it would be in the feces. Parasites can also cause blockages at times.
Calcium imbalances can cause muscles to be weak which might make it difficult to pass feces. Its important that she gets enough UVB to produce vitamin D3 so that she can use the calcium you provide for her. The calcium is supplied by dusting the crickets two or three times a week lightly with calcium powder (that does not contain phosphorous). Insects have a poor ratio of calcium to phosphorous so this helps make up for it.
Mine get no direct sunlight (it can't pass through glass or plastic...and the UVB light shouldn't either) so I dust lightly twice a month with a vitamin D3/calcium powder.
I also dust lightly twice a month with a vitamin/mineral powder (that contains vitamin A from a beta carotene source). Temperature must be within the appropriate range so she can digest her food and absorb nutrients.
Insects should be gutloaded before feeding them to the chameleon too.
If the blood continues to be passed and the feces/straining situation doesn't clear up quickly, I think she should see a vet.