BD's gf disciplining your child?

I know a lot of women are bitter that the fathers of their children have moved on and are in relationships with other women . With that being said, what are your views on the baby daddy's girlfriend disciplining your child? Say this woman is on good terms with you, has your child 4 days a week, takes care of them 100 percent when they are in your care? What if the real mom never even bathes her child or spends time with them? Disciplining meaning possible spanking/tapping their behind if they do something wrong or even putting them in time out?

Yes this is my situation. I have been a step mother figure for 3 years to this child, yet I have been told I am not allowed to discipline the child. I feed, bathe,take the child to school, and everything under the sun that a mother would do.....yet I am not allowed to discipline the kid when they are with me ? What am I, a maid?

What are your thoughts ?

**Also, the mom is an alcoholic with DUIs, spanks the child often. I however am a nuturing woman with love for every child I meet. I was abused as a child and spanking is not something I do. I was literally warned by the mother to never spank her kid. The kid is a toddler who lied and told her mom that I spanked her. I never touched her. So I feel like the mom just made this up to cause problems between the father and I