https://roachforum.com/threads/female-dubia-with-vent-issues-possible-prolapse.9821/
Here's something similar. Hope it helps
There are lots of similar posts and I read three or four with all the same advice
She is a hisser, yes?
If so than what she may be doing is "airing out" her ootheca. It is kind of difficult to see in that photo to be honest. Hopefully that's all it is, and it is normal for her to do so once mature and breeding.
I've never really had this exact issue thankfully. I'd probably try placing small apple pieces all over their bin and then throw them away later that day or the next day then put fresh apple pieces and repeat in hopes that you throw away most of the mites on apple pieces.
At the same time I'd...
I want to say that they have specialized piercing mouthparts when young used to pierce mom and slurp/drink. Said mouthparts are lost at some point. It is very crazy cool!
Mine are in a slump unfortunately- I need to pay them more attention.