I need help!!

I need some opinions. What is the best way to parent a 4 year old if you are the stepmother? I find it difficult because when it comes to discipline I don't know what I should be able to do. I feel like I should be able to do whatever my husband does for punishment but the mother feels like I have no right at all. I watch her all the time when she is with us and I will not let a child run all over me so I do put her in time out and correct her. I feel like that is within my rights. What are your opinions?