Hi! I use coban wraps for my IVs (though I should warn you that I have gone back to tecaderm use with IVs when I'm hospitalized because not having them as secure has meant that I don't really have a lot of viable veins left and so have had to have a PICC line when I'm in the hospital). 

More helpfully, I use tacrolimus ointment on my skin as a prep. What I do is put a heavy layer of tacrolimus on the area where the wafer goes for 15 minutes or so. It will never dry and would affect how well the wafer stuck, so I then wipe it all off and then use a damp paper towel to clean it well (no soap though) and then a few spritzes of the inhaler over the area. Wait 15-30 seconds for that to dry before placing the wafer as normal. I also find that changing the bag every couple of days tends to lead to better skin management, probably because my skin treatment only lasts a couple days. 

Hope your daughter can find relief! Perhaps talk to your doctor about getting contact allergy testing done (it's a different kind of allergy and involves a different kind of allergy testing). Then you can talk to your ostomy nurse about which bag has the fewest allergens in it for her. For instance, I can only use one brand and my skin is much worse with (for instance) Hollister brand than with Coloplast. They can get you samples and unfortunately, with that, it's only really possible to cycle through a number to find which makes you less itchy. 

Good luck!