Find out why she’s angry. Start by finding out if her anger is even valid. Determine if it is something you did, a miscommunication or more. You’re going to need a bit of patience to get through to her, as her anger will likely not fade easily. If she absolutely won’t text you, communicate with her friends to get to the bottom of why she’s so angry.
Apologize. If you're in the wrong, and you should know if you are, start your text by saying you’re sorry. Don’t patronize her or pressure her with guilt or the threat of starting up another argument. Instead, draft your text to say something like, “So sorry I hurt you. I just want to know how you feel and if there’s anything I can do to make things right again.” If she hasn’t completely blocked you, she’s getting your texts and is just ignoring them. Starting off with an apology sets the tone that you’re not trying to stir up old feelings or ignite an argument, rather that you’re trying to fix things to make it better.
Be nice. She’s probably still upset and hurt by whatever happened so you’re going to need quite a bit of patience to get back in the game. Be as nice as you can by texting her to see how her day was, if she’s feeling better or to ask her know if there’s anything you can do for her. Don’t lay it on too thick. You don’t want to come off as phony, and if she concludes that you're not being authentic, it’s going to mean trouble.
Be sweet. Be better than nice by being sweet. Follow your normal texts of “just texting to say hi,” with, “I stopped by the bookstore and picked up your order that came in and dropped it off on your porch,” or, “You’re beautiful and I miss you.” Again, being genuine and real is what is going to show her you’re serious, so be careful to only text what you mean.
Be persistent. Keep going. Don’t give up. With women, you’re likely to be right on the edge of a breakthrough before you reach success, so keep it up and don’t fade away when some of your attempts are unsuccessful. Part of the process in her ignoring you is to see how far you’ll go to make things better. Show her you’re the bigger person in the situation and don’t let her go.
Apologize again. Take another stab at "I'm sorry". You can never say you’re sorry enough, so if she starts communicating with you a bit, more, remind her that that you’re really sorry. Show her you’re sorry by actually doing better. Take things slow as she starts to open back up so you’re not pressuring her to like you again.
Text something funny. Try something like, “Do you think you’ll ever like me again? Text yes or no.” This funny little question is so juvenile, it may make her realize the reason why she’s angry isn’t that big of a deal and give in a little. Making her smile with your cute wittiness will help her remember some of your better traits and might help her to give in.