I do so much for her and her family, and she continues to hurt me with her words.
PattyD, My suggestion is to do a lot less for her and her family. Change the pattern. Change the input to change the output.
You have 3 children, why not spend more time with the other two and friends? I don't have a suggestion about her taking your access to the grandchildren away, except to offer to babysit other children.
If your daughter deals with everyone via text message because she is so busy, you do have to choice to not read the texts. Deal with whoever you want to in the "real" word, the cyber world, texting, Facebook etc. etc. can be an easy way to put up barriers and keep people at a distance. Let her text her hurtful words to someone else. You don't have to accept the hurt that she's offering you.
Have a relationship with the people who actually want to speak to you.
If you are always at odds, that takes up a lot of energy, I sure would be tired of someone only dealing with me via texts.
Your daughter appears to be telling you how the relationship will be conducted. On her terms. It's her way or she will resort to threats. Sadly, it's a similar story for many people here, whether or not you choose to accept her terms is up to you.
You can't get a previous relationship back, people evolve over time and family members don't always evolve in the same direction or at the same time. Don't worry, you'll make it through, times like this can be enough to get you panicky.