Pooping problem

by Melissa
(Malaysia)

Hello, my name is melissa and i have a amboina box turtle and her name is Luna. I had had her for about 5 years and i've never encountered any problems with her so far. But recently, i have noticed that, there is a very weird and scary thing poking out of her anus when she poops. The first time i saw it, i thought it was her poop. It was as large as thumb and it was black and shiny. It only happens when she poops. She is eating fine, as usual, and appears to be as healthy as she was since i got her. And when i examined her after the incident, around her anus, the skin looked red, you know. I imagined she might be having a constipation problem, but so far, i've been feeding her tortoises food bought from local stores, and she has plenty of water all the time. So, im pretty worried about whats happening. All i know is that there's this black slimy thumb size thing that protrudes out of her anus whenever she poops. Her poop is normal, its dark orange colour and soft (but not watery).

Please help me, im really worried about her. Thank you guys :)