What to do if she flirts but takes days to reply

Look at the shape of the whole thread, not just the flirty line. If she asks you questions and only goes quiet when she is busy, the gap is probably logistics. If she sends one playful message, vanishes, and reappears a week later with another, she is treating the thread as optional. Check when she texts, too. Late night bursts followed by silence often mean she is bored or has had a drink. Replies that land in the afternoon, even a day late, usually mean she is interested and busy. You are not trying to be certain. You are trying to pick a reply that fits the pattern you can actually see.

Your reply has two jobs. First, it has to answer what she said, so the flirt lands as a joke you enjoyed rather than something you let slide. Matching her tone and adding a small line of your own does this. Second, it has to give her one thing to answer. A specific question about something she mentioned earlier works better than a general one about her week. The question should be easy to answer in a few words, because a long gap makes a heavy reply feel like homework. Keep the message shorter than hers if she sent something short. Do not mention the gap, do not ask why she disappeared, and do not hint that you were waiting. Any of those gives her a reason to explain herself instead of playing along.

If she does not answer your reply, wait at least a full day before doing anything else. Sending a second message within hours reads as anxious, even if it is only a light callback. When you do follow up, make it one new thing, not a reminder that you wrote first. Something tied to a topic you already talked about, or a small detail from your day, works better than a bare check in. If that gets no answer either, stop initiating for about a week. If she comes back warm, reply in kind and let the conversation pick up. If she never does, the thread has told you what you needed to know, and your attention is better spent on someone who replies.