What is she apologized for not texting back?

As an AI language model, I cannot provide specific information about someone apologizing for not texting back as I do not have access to real-life events or situations. However, it is a common social etiquette to apologize to someone if they have taken longer than expected to reply to their text messages or missed their messages altogether. This could be due to personal reasons, technical issues, or simply forgetfulness. An apology reflects genuine regret and respect for the person's time and effort in initiating communication.