As generations grow and develop over the course of time, many things will also grow and develop at the same rate. This is usually because society norms and technology are changing so much that it's often hard to keep up with it all. Moreover, it's can also be difficult to accept things changing in the first place. People are often set in their ways for one reason or another, whereas others want to accept new changes that they see fit for their life.
This is especially true when it comes to parenting. Baby boomers are often seen as harsh and strict when parenting their children, forcing them to stay in line all the time. Yet their millennial counterparts are considered to be softer and more considerate in their parenting style, as well as able to question their parents or surroundings. This sharp contrast can often create friction between generations, such as between mother and daughter. The daughter thinks that her method is correct, yet her mother believes that it's wrong. How can you get mom to stop criticizing your parenting style? Is it possible to get her to accept how you're parenting your child?
The biggest thing to do is to take your mother aside and explain that you and your family are content with how things are when it concerns parenting. Also, explain that what she might see as a lack of discipline, for example, is just your way of enforcing ideals in a different way. Some of the ways you were punished might not work for your family, or shouldn't even be allowed under any circumstances. One example of the latter would be spanking your child due to the negative effects it will bring on.
As for mom accepting your parenting, it's not something you should hold your breath for. Your mother may very well be stuck in her ways and refuse to accept your parenting method, let alone your explanation as to why you're doing it. But be firm when you tell her that she needs to accept your choice of parenting style.
You should also be firm if she tries to criticize your parenting in front of your child. Express to her how it undermines your authority as a parent when she does that. If she really wants to critique you, she can do so in private, far away from your child's eyes and ears. It's just the polite thing to do.
In the end, you'll most likely find that you two are unable to find a middle ground on the matter. That's honestly okay. The best thing for your mother is to, at the very least, respect your parenting style. It's okay to agree to disagree, so long as it doesn't negatively affect your relationship with your mother. It might not be easy, but it will benefit the two of you in the long run.