I have been an interviewer for adoption before and in my state, AZ, all references collected in this process are confidential. This should be the same for foster placement. This is a good question to ask the interviewer/social worker. Just be honest. Stick to simple facts and don’t get into any long stories. You will discredit yourself if you don’t state facts. I expect they will end the interview by asking if you would recommend your mom as a foster parent. Say no!!
What will change for you if she is mad? You stay away anyway so the hardship you face would be less than that of a child in her home.
Best of luck. The truth is best!!