I think it's first important to realize people do the best they can...I truly believe that. These are your mom's tools to deal with life. Controlling people tend to be anxious people. If they can just move people around like chess pieces, their anxiety is in check. I suspect your mother had a tough childhood...maybe a childhood where she felt very out of control (alcoholic home, abuse etc.) and also had poor coping skills modeled for her. I say this not to give your mother excuses for her behavior...but for your understanding. It's important to realize many of the people we love are sick in their own ways. They do the best they can with the skills they have...which often cross other people's boundaries. That insight can help you with forgiveness rather than anger, understanding rather than resentment. This will be important for you in order to set boundaries with your mother in healthy ways.
First, you must decide if you want your mother to be a part of your life. You are not obligated to interact with her. You are not obligated to accept her calls or read her emails. Often these situations take some sort of shock event to get someone to be willing to change...to look at things in new ways. We teach people how to treat us. You have taught her that it's ok to manipulate...because you haven't set consistent, healthy boundaries with her.
The healthy thing to do in this situation would be to write a heart felt email. It shouldn't be angry but caring and direct. I wouldn't do this by phone or in person yet. It would likely escalate and it's much harder to think on your feet. The email could start by talking about all the things you love about her...things you appreciate about her...things you are thankful for that she has brought into your life. You could talk about how you want her in your life and in your child's life. Then you get into some of your issues with her...ie her need to treat you as a child rather than a woman...her actions which feel demeaning...talk about exactly what you see. I wouldn't use this as an opportunity to beat her with your childhood but to look at her actions now which make you feel less than.
After you have spelled these things out is when you set healthy boundaries that you are comfortable with...and possibly take some time off from each other. If she wants to be a part of your life and her grandchild's life she needs to conduct herself in ways respectful of you as her adult child. If she can not, then she can not be a part of your life. The time away will give some clarity to that reality. You can even ask her to get some help, some therapy. It's much like an intervention for a drug addict..."we need you to get some help or these are the consequences". You are not obligated to spend another minute with her...and she needs to know you are willing to cut her off. I suspect the prospect of that will terrify her, and she may be willing to look at her actions. If not, then she has made her choice...she chooses her victimhood over you. She chooses her drug of choice...manipulation over her grandchild. I wouldn't go back and forth with her...just email, maybe one clarification email then be done with it...let her sit on it. She what she does with it.
Without a major gut check your mother will not be willing to change. You must set healthy boundaries with her or this will get worse. Wait until the grandchild is born and she is trying to take over as mother. It will happen. So setting these boundaries now will in the long run help all parties involved.