My girlfriend asked me to text her every morning.

You can ask her if she had breakfast in the morning and what she ate. You can also tell her that what she eats is nutritious and healthy. Of course, asking these questions every day is also annoying. You can ask her if she slept well last night, tell her how you slept and what dreams you had, tell her what you are going to do today, and say something sweet. Actually, you can send anything you want. Now that you have promised, you must do it. If you forget one day, apologize afterwards.