Is it disrespectful to not reply to a message?

Start by rereading her message and asking whether it needed an answer. A question about your weekend, an invitation, or a comment that clearly wants a response all count. A photo with a caption or a simple 'hey' is more relaxed and can sit a day or two without anyone being hurt by it.

The length of the gap matters too. A few hours of quiet is normal. Two or three days with an open question starts to read as not interested or as forgetting. If you know you are not going to answer, the decent move is still a short reply, even one that says you are not feeling the connection.

When you do reply, respond to what she wrote first. If she asked about climbing, say whether you climb and what you usually do. Only after that should you ask her something back, and make it about the thing she just told you.

The reply should be shaped like a real answer with a small hook at the end. If it is a plain acknowledgment, make sure it still gives her a reason to keep talking, or make clear you are wrapping up. Keep the tone easy and avoid over-explaining why you were slow.

Timing says as much as the words do. A reply that arrives the next afternoon reads as normal life. One that shows up at midnight after a week of silence can look like a reach, and a reply sent the same minute after a long delay can look like you were waiting.

If you have already gone quiet for days, do not send a flurry of messages to catch up. One reply is enough. If she answers warmly, continue. If she does not respond after a reasonable window, around a few days, let it go. Sending a third nudge tends to make the silence about you.