Hi, I need help answering this message from a girl in my class.

So basically, I wrote a little note card saying whether she wanted to hang out with me at the Christmas market. She liked my neat handwriting (it was in Japanese), and she declined. We met each other for three years at high school, and I haven’t talked to her much. Is “Okay, no problem!” the best answer, or there are better ways to answer it? I know it isn’t the end, so I need some advice.