Asking if she's lost interest: when it's fine and how to do it

Before you decide to ask, look at the pattern. One slow reply means almost nothing. Plenty of people go quiet for a day because work ate them. What you're looking for is a shift that has lasted several days: replies getting shorter, questions she used to ask stopping, plans going from firm to vague, and the initiative moving entirely onto you. If you're seeing that, the question is reasonable. If the whole thing is one odd afternoon, asking will make it look like you're the one with the problem.

Also look at what's happened to the momentum. Did she used to bring up things you'd said earlier? Did she suggest things? If she still does those things and only the speed has changed, she may just be busier. If the content has gone thin along with the pace, that tells you more than the timing does. Ask yourself whether you'd be okay hearing a yes, because that's the answer you'll get some of the time.

A question like this lands well only if it's clear you already know that what you're hoping for isn't a reassurance trade. Name what you noticed in plain terms, one observation, not a list of grievances. Pointing out the slower replies and the plan that got pushed back is specific and fair. Then ask the direct question once, without a rider. Adding "or is it just me" or "no pressure if not" weakens it, because it tells her you want the question taken back.

The move here is to make an honest answer easy to give. If she says she's been busy and not very into planning, you'll know where you stand and can decide what to do. If she says she's still interested, you'll have an answer to act on rather than a feeling to chase. Either way, the question has done its job. It isn't supposed to produce the feeling you want in the moment.

When you send matters almost as much as what you send. A late-night message reads as anxious, even if the content is calm, because it suggests you've been stewing. Send it in the middle of the day, when you're not waiting on anything in particular and would be fine either way. Avoid sending it right after you've seen her online but haven't gotten a reply, since that makes it look like you're reacting to her behavior.

If she replies with something short or noncommittal, don't follow up within the hour with a second version. Give it a day. If she answers honestly and the answer is that she's lost interest, reply with a short, gracious close and stop. If she doesn't answer at all after a day or two, that's an answer too. Don't send a second question. Let the thread sit, and decide whether you want to keep going based on what you've already learned from the first one.