How to handle a breakup maturely?

My girlfriend and I broke up on Saturday mainly because she said to me that she didn't feel the same about me. So, I departed and shortly after she texted me saying that she felt bad and that she hoped we could still be friends. I have yet to respond back to her text message. I am not in the utmost rage or anything, but simply disappointed. I want to reply back to her text maturely and honestly by claiming that I don't want to be her friend without making matters worse, because platonic friendships never work in my book. What do you think guys?