Hi Sally,
I am so sorry to hear about your niece, and I think it is beautiful that you are being proactive and looking for support for her.
Have you tried searching on Facebook? There are so many support groups out there and I'm sure there has to be one for teens. If not, I know there are support groups for those living with a stoma and through there I'm positive you or her can connect with someone near her age.
Always dancing,
Elizabeth (team member)