Here is something that may help!
I suffered from the similar your daughter suffers from, that internal nasty burning, of which mine was extremely painful to say the least. This is Rx only, so her Gastroenterologist or Attending Physician will need to prescribe--> [Lidocaine Hydrochloride Jelly USP 2%], the product itself is sterile and comes in 30 ml tubes. It's a little on the expensive side but most Insurance providers will cover or a good portion of.
My Gastroenterologist PA started me on this after my total colectomy w/j-pouch in 2004. Although the sits-baths, calmoseptine and Metamucil helped, the Lidocaine Hydrochloride Jelly USP 2% did the trick.
Method of application: latex or similar type glove, apply a generous amount onto (a) finger then insert into rectum/area where pain is initiating. The tubes also include an applicator ea., that attaches to the tube for an alternative method to apply.
I used it after ea bowel movement, the relief was substantial. It's worth noting, the relief is by the numbing effect from this product, there may be some stool leakage after using due to it's numbing effect although it was minimal, at least in my case, and the benefits far out weigh the negative. Wearing a liner i.e., Depends helps in preventing staining.
I've tried other forms of Lidocaine, different from the product I mentioned above but the stinging was painful and lasted longer upon applying, and the relief wasn't near as good or last as long as the product I'm mentioning here, and with just a slight sting that lasted only a second or two.
I've found over the years discussing the good, bad and ugly on this topic in general that everyone responds differently when using the products mentioned in this discussion, all of which are excellent. So it does take some experimenting using these products be it single use or a combination of to find maximum relief.
Daily Metamucil intake is key, at least it is in my case. Metamucil is an excellent source of fiber; in the case we're discussing here it's very beneficial in that it's binds itself to [Bile], the primary cause of 'butt burn'. Bile is a given, is an important component in the Gastro/Digestive tract so it can not be eliminated or reduced, that's where the Metamucil comes into to play. I'm a daily user of Metamucil; without a colon/large bowel, [Bile] is ever present when passing stool, thus the after affects result in butt/rectum burn which Metamucil certainly helps to reduce.
I suggest taking Metamucil throughout the day vs once a day and suggest a dose prior to retiring for the nite. I take Met with a meal and also by itself at times, just my preference. My current to date daily intake of Met is 2-3 teaspoons in 16 ozs of water three (3) X's p/day. I stir vigorously then immediately drink it. I found this method/dose works best for me, it is not a standard dose by any means. Everyone responds differently to Metamucil, suggest to start with a small amount and work from there until desired results are achieved. If taking OTC and or prescribed medication, including vitamins, Metamucil should be taken two (2) hrs prior or two (2) hrs after taking meds/vitamins to lessen it's binding effect.
Calmoseptine is an excellent product to fight butt burn, but the Lidocaine product I mentioned works best for relieving internal burn, it also can be applied on the exterior skin although I found Calmoseptine worked best in that respect when applied on the exterior. Hope you find some of this helpful! Best Regards!
