He forgot that she had a food allergy. How can he make it up to her?

“I invited my girlfriend over for dinner to make her a home-cooked meal to celebrate our two month anniversary. When we started eating, she had an allergic reaction and left immediately. She texted me later asking how I could forget that she was allergic to peanuts, which I totally forgot about. Now she won’t respond to my messages. How can I make it up to her?”