You can't change her. She has this type of personality (which is a lot more about control than about pure concern). You tried to stop it at 21, and now at 43 it's still going on. So whatever you've been doing hasn't worked. The definition of insanity is continuing to do things the same way while expecting different results.
If she doesn't get her way and decides to be all pissy with you, that's HER choice. If she has no activities, no friends, no interests beyond you and your daily activities, that's HER choice. You have enabled her for years and it's going to be harder and harder to break this if you continue. When she is really old and infirm, it's going to be horrible for you.
I would write her a letter and lay out your reasons, and tell her what this does to you. Tell her it makes you RESENT her and want to AVOID her; it doesn't make you feel loved or cared for or concerned about. Tell her it's the exact opposite of how you are raising your kids, that you have sworn you won't do this to your kids. Meantime, your children see you as being walked on by someone else. Do you want them to grow up resenting their grandmother, and having a role model mother as someone with no self-respect or backbone? Tell your mom this.
Tell her (and do this...) that you have an "in case of emergency" card in your wallet and a listing in your cell phone, with her name as your mother. If anything happens on the road or on vacation (Good Lord, on your honeymoon???), emergency services will look for that info and call her. Perhaps the only exception is if you leave in bad weather.
I have always let my family know when I am out of town - we all do it. We send flight info, dates, and hotel info by snail mail or email. If your mom wants to call the airlines to see if your flight arrived safely, let her. Does she have email? If so, send her a quick "home safe" message and DO NOT REPLY if she responds by email. If she calls your house, do not answer the phone if you know it's her attempt to engage you in details. You have to put the kids to bed, start the post-vacation laundry, whatever. Let her know that this is what you do every time you come home from a visit, and you have no time to discuss what the kids did in the car to pass the time. The older your kids get, the more of this they will see and incorporate into their own lives, either by repeating the behavior or by getting walked on by someone else because they've seen you do it and think it's normal to be miserable and manipulated.
You really have to do tough love on this one. She's not actually making you feel bad. YOU are letting YOURSELF feel bad because you cannot control her, and you (so far) cannot control your reaction to her.
One other thing you can do is to consider some short-term counseling to sort out your feelings about your mother, your resentment, your feelings of not being in control of your own life, etc. Together, you and a counselor experienced in this area can develop some strategies to change this destructive pattern.