So my niece is looking for a job and my sister wants me to help find her one. She would like to do modeling but most of those are scams. Does anyone know any reliable companies?

Other than that, she can do pretty much anything. Her dad doesn't like the idea of dog walking or particularly baby sitting.

Any ideas? I don't want to give out details but she is looking for quite a bit of money so she can save up for a blackberry, she doesn't get pocket money and won't get paid for jobs around the house.

Please don't ask questions I just need to find her a job!

Seems some confusion here as a few minutes later you post as an 11 year old girl.
https://www.askmehelpdesk.com/other-careers/11-year-old-jobs-girls-642285.html#post3067101
So which is it ?

At 11 in the UK there is very little legally available in any field.