Like nssg, I'm confused by what you mean by bags 'bursting'. I've had bags absolutely full to straining point, but none of them have burst. Once a wafer popped off and the contents spilled all over me and my bed, but that was my fault: I just couldn't be bothered getting out of bed to empty the bag and left it too long.
Modern bags shouldn't burst and they don't easily tear or rip. Most leaks occur somewhere along the wafer - the wafers are more of a weak point than the bag.
If your mum is emptying her bag 3x a night that sounds like she might have high output. There is a technical definition of high output (it's having more than 1500ml of output in 24 hours, I think), and the stoma nurse ought to measure it. If she does have high output, the GI needs to find out what's causing it.
The stoma needs to be checked as well. If it's too retracted or lies too close to the skin, that can be a big problem. Stomas ideally should stick out by 1 to 1.5 inches from the stomach. This makes it much easier for all of the output to empty into the bag, instead of some of it getting trapped underneath the wafer.
I don't think a hernia by itself would cause leaks. But if it changes the contour of the stomach in such a way that the wafers no longer lie flat or have wrinkles in them, then, yeah, that could cause leaks. Likewise, if your mum has gained or lost weight - that could change the shape of her stomach or the size of her stoma. One thing the stoma nurse ought to take a look at is the hole in your mum's wafers and how well it fits around the stoma - does your mum cut her own holes or do the manufacturers do it? It's important to get the hole to fit the stoma as closely as possible.
Good luck, UB. I'm glad your mum is seeing a GI, because she shouldn't have to live like this.
Dx Crohn's in June 2000. (Yay )
Tried: 5-ASAs, azathioprine, 6MP, Remicade, methotrexate, Humira, diets.
1st surgery 20/2/13 - subtotal colectomy with end ileostomy.
2nd surgery 10/7/15 - ileorectal anastomosis. Stoma reversed and ileum connected to the rectum.
Current status: Chronic flare. Do I have any other kind?
Current meds: 50mg 6MP; Entyvio (started 3/11/16)