I read the story and reviewed the pictures and do not understand how a person could voluntarily do that to their self.
In the past, I have been into hot water enemas of a galloon of water. I used an aquarium thermometer to measure the temperatures. I find:
Temperatures of 105F to 110F are warm to tolerably hot. Keep in mind that certain candies & foods can be cooked at 111F!
A temperature of about 115F is about the maximum one can tolerate. You can shower in 115F water once you get use to it.
A temperature of 118F is really painful! And 120F is agonizing!
I had an elaborate system where I used a panty girdle to hold the enema nozzle, in place and in me. I would tie myself up on the floor and lock my hands over my head. The keys would be on a long string across the floor. It would take me several minutes to reel in the key and unlock myself.
I had a release string to pull the enema clamp and release the water. But, I found the pain of 120F was too intense, too fast and I could not just pull the release. I found an old mechanical camera remote release. Tied that to the enema clamp. It allowed a 30 second delay from when I triggered it until the mechanical timer released the enema clamp. 30 seconds was enough time to allow me to disassociate triggering the timer and the start of the agonizing pain. I am a masochist and - - - enjoy the pain!
The nozzle I used was an antique, multi-directional vaginal douche spray nozzle. The hot water spray was like needles of pain inside me! My body arched in agony and gave off an acrid fear-sweat. The gallon of hot water would flow into me before I could reel in the keys, unlock and untie myself. Then I would rush to the toilette and expel. The hot water went in, past the anus. But it burned painfully to gush out through the anus!
While I did seek out the agony, it was not very safe. It drew blood from inside my rectum. (Not a good place to cause blood wounds.) I read somewhere that cooking your rectum with hot water could be fatal.
DON'T TRY THIS AT HOME KIDS! I'M AN IDIOT!
I have no idea how the woman in this article got these wounds. Especially self inflicted. I am inclined to think she had an abuser who injured her.
Here in the USA the water temperature from the faucet, especially in apartment buildings, is often set to 135F, which is hot enough to scald and cause serious in jury. Every few years there are articles about some parent who scalds their baby to death dunking it in a hot bathtub as a punishment.
I've never used glycerin, so can't advise about that.