Hi Bethie,
Learning the process and technique of appliance changes can be confusing and frustrating. It sounds as if she has a bit of skin irritation, most likely due to output getting under the wafer. Does she have an end ileostomy or a loop? I find the end ileo to be much more manageable and easier to fit because it generally sticks out a bit further than the loop. First, you really need to make sure you are measuring the stoma before putting on a new wafer. I don't know how long it's been since the surgery, but the stoma does shrink considerably over time. If the hole in the wafer is too large, stool will be in direct contact with the skin. Also, is the "adapter ring" you are referring to an eakin ring? This goes on before applying the wafer. This will give a much tighter fit, and I have found, helps considerably with skin irritation. It may seem as if it's swallowing the stoma, but if output is normal and she is not experiencing discomfort, it should be OK. In terms of the powder, the kind I use doesn't require any prep. I simply sprinkle the powder over the red, irritated areas before putting on the wafer. Maybe you have a different kind?
Does your hospital have more than one ostomy nurse? They should have gone over the ordering process for supplies with you before discharging you from the hospital. If not, do you have a post-op appointment already scheduled? I usually see my ostomy nurse in conjunction with my appointments with my surgeon. I was give a catalog, and my nurse flagged the pages of the supplies I would need. You should call the nurse if you are unsure of anything in terms of process, as they are there to help you.
Best of luck!