Boundaries is the issue here. As parents we gradually loosen the boundaries. There is no certain age to stop parenting. We gradually do it.
But then, what is the definition of parenting? I suggest that once a child moves out of the house to be on their own we stop calling to make sure they're wearing a sweater. lol But then is that parenting?
My grandchildren are now 9 and 12 and we still insist that they wear sweaters. I'm trying to stop doing that. They're old enough to know whether or not they need one. And whether or not a person needs a sweater is best known by each individual. All of us have different metabolisms and sensitivities.
My parents always were interested in my well being. They offered advice and my mother allowed me to take it or not. My Dad insisted he was always right and lectured me when I didn't do as he said. I appreciated my mom and fought often with my dad. Boundaries were frequently an issue with both.
My daughter moved out and was pregnant at 19 while still relying on my for financial support. I continued to parent, i.e. teach (as I saw it) how to live as an adult. We fought a lot. Eventually, taking a few years, we both learned how to have better boundaries. I learned to let go of my need to control her. Of course, I didn't see what I was doing as control but it was. I had to learn to let her make her own mistakes. I learned to only offer advice when she asked for it. And I learned that if I couldn't give her the money without strings attached I had to not give her the money. We had to take a break from each other of a few weeks to 2-3 months before we learned how to be friends.
It's not always a smooth transition from parenting to being a friend. In fact I suggest that it's often very difficult as pictured on this site with all the parent and in-law questions. The theme I see running thru all of them is needing boundaries. Learning to have and keep boundaries is learned from childhood on. Parents and children can be friends once all people have boundaries and recognize the other person's boundaries. It's an ongoing learning process and doesn't stop until we die.
I recognize that even friends often have difficulty with boundaries. I have a friend who worries and expresses her concern that I'm over doing with my daughter and her family. My sense is that she feels that I'm not doing this the best way. And she may be right but what I do is my decision. I sometimes resent her comments but I still briefly listen before changing the subject while I consciously let go of my resentment.
With my friend I've tried telling her I don't want to hear it and she doesn't get it. I've decided to not make that an issue in our friendship. I can see doing that within the family too. As you said your mom does this out of love. We cannot change the other person.
Now with my daughter, we've learned to be more direct and both of us will say that we don't want to hear it. We've also learned to say when we just want to vent and don't want advice. Good communication makes good boundary enforcement.
First we have to know what our boundaries are and then we need to learn how to thoughtfully enforce them It's more complicated between parent and child but it's important to work on it.
My daughter says I'm not her parent now. I'm her friend. But she also says I'm her Mom. I think she's right but it's a very difficult concept to get my mind around. That's a whole nother post.