I really upset my friend, what's the best course of action?

It was a petty comment regarding Adolph Hitler that I think she took the wrong way. She won't answer my two apologetic texts that I sent. Oh, she's 15 by the way and Jewish. I've never done anything like this before and I don't wanna ruin our great relationship. My comment was not blatantly offensive, but I realized it could be interpreted in a very wrong way. What do I do? Let things cool overnight?