Your sister should have a court-appointed attorney who would be looking into the lack of proper notice issue if appropriate.
Attorney Inga Stevens is licensed in Maine. She provides general information on Avvo.com. No attorney-client relationship arises out of the information given here.
She probably already has a court appointed attorney. In Arizona most parents qualify for public defense services when there are dependency proceedings. It may be advisable for you, as her sibling to consult with legal counsel for yourself. CPS should vet placing the child with you as a 'kin' placement. This does not fix the problem, but it may slow down the process in order for your sister to demonstrate that she is sober...and without the risk of well intentioned foster parents falling in love with the child and wanting to adopt.
If your family is willing to help, it may be advisable to consider private counsel for your sister. Sometimes having extra attention (perhaps more than the public defender can give) is the difference between a severance and a reunification. www.woodnicklaw.com
Here are a few links that might be helpful:
This general information does not create an attorney client relationship between the questioner and the author. The internet is NOT a place to get 'legal advice'...although gathering general information is always helpful.
Sign up to receive a 3-part series of useful information and advice about child custody law.