There is actually a scientific name for this, which I think is casually called "Rapunzel Syndrome." Hope you find answers and some coping mechanisms :)

I’m sorry I don’t have an answer about the constipation from hair chewing. I just wanted to say that the hair chewing is likely due to anxiety & if you can help ease her anxiety then this could also control the hair chewing. If she has an OT, she can provide your daughter a sensory diet which would give her tools to help calm her when her anxiety is high. I hope the Dr. has a solution to end the bloody stools.