How to reply when she says she's training for a marathon this weekend

She is telling you what her weekend looks like. A 20 mile long run on a Sunday means her Saturday night is probably quiet and early, and her Sunday morning is spoken for. That is information about her schedule and her energy, not a verdict on whether she likes you. Most people who train seriously plan around the run for weeks, so mentioning it is often just her being honest about why she can't do something spontaneous.

So read the message as a sketch of her life. She runs, she has goals, and she's comfortable saying so. The useful question is not whether she is interested in you but whether she wants to fit something in around the run. Her wording will usually tell you. If she mentions the run as a reason she can't do a specific plan, she's signalling the week, not closing the door.

The reply that works starts by showing you actually took in the detail. You can name the run, or the distance, in your own words and say something about what that takes, without performing expertise. Keep it short and let her decide how far to take it. A reply that is mostly a warm acknowledgement with one open thread is enough, because it lets her reply with more about the training if she wants to, and it doesn't force her to manage your curiosity.

What to leave out: specific running jargon you'd have to google, any comparison to your own fitness, and any question that asks her to justify or explain her schedule. The point is to make her feel heard about the thing she mentioned, not to demonstrate that you're also a runner. If you want to ask something, keep it about her experience of the training, not about times or technique.

Once she's said the weekend is taken up, don't push a plan into it. Send the acknowledgement, and if you want to see her, suggest something for the week after the race or the following weekend, ideally with a rough day so she can say yes without checking. Sending the plan straight away while she's clearly focused on training reads as not listening. Waiting until she's free is a simple way to show you took her schedule seriously.

If she doesn't reply for a few days, that's normal around a big run and says little about interest. Send a short follow-up after the run, asking how it went. That gives her an easy reason to talk and shows you remembered. If she still goes quiet after that, let it drop for now rather than sending a second nudge. A serious training block often means a busy stretch, and the conversation can pick up again without you chasing it.