First, congratulations on all your considerable achievements. You have every right to be proud of yourself.
You are suffering because you are caught in a generational divide. Your mother wants you to repeat the life she led, staying near her parents. You are in America where there is more emphasis on individualism. You are not going to change her. She is not going to change you. Your mother has made it clear that you can’t win so stop trying to. Although your suffering shows how much you do care about your mother’s feelings, it isn’t getting you – or her – anywhere.
There is no need for screaming and crying. Screaming and crying tells your mother that you might be coerced into doing as she wishes. Clear decisions are stated with calm certainty. Make a promise to yourself that you will stop your end of the fight. If your mother makes accusations or statements meant to provoke guilt, you can tell her you love her very much but that it’s time for you to grow up and move on. Reassure her that you will certainly want her to be part of your life in some way, especially when you marry and have children. Let her know that her blessing and her pride in you mean a great deal but that you need to look to your future, not her past. You gave her what she wanted in your choice of undergrad school. Now it’s her turn to support you in doing what you want to do for graduate work.
Your best ally in this situation should be your dad. When adult children leave home, there is often opportunity for the parents to rekindle their relationship. Your mother’s focus is still on being a mother of a young person, not on being a partner for her husband.Your dad could help a great deal if he would court her a little and tell her how much he is looking forward to having her all to himself again. Perhaps that will help her shift her attention back to where it belongs — with her husband. I suggest you talk to him adult to adult and ask for his assistance in helping your mother through this difficult transition.
I wish you well.