Why do people respond with one word answers?

The same word means different things depending on what it answered. If you asked a question that needed a real answer, like where she grew up or what she does on weekends, and she replied with yes, that is a clear signal that the question was too narrow or too closed. If you sent something funny or warm and she sent lol, she probably enjoyed it and had nothing to add. Look at the length of your last message too. A long message followed by a short reply usually means she felt the pressure to match effort and could not. A short message followed by a short reply usually means both of you are in low gear, which is fine.

Also look at how fast she replied. A quick one word answer is often a sign of someone who is engaged but short on words that moment. A slow one word answer, sent hours later, is more often a sign of someone who is using the app in gaps and is not prioritising it. Neither one tells you she is out, but the second tells you the conversation is not her main thing right now, so your messages should be easier to answer, not harder.

There are roughly two kinds of reply that move a one word exchange forward. The first is a choice question, where you offer two options and she picks one. This works because picking is almost free to do, and it still gives you information about her. The second is a small callback, where you return to something she said or showed you and ask for one more detail about it. This works because she has already done the thinking about that topic, so the cost of answering is low and she gets to talk about something she likes.

A draft is in the right shape when it could be answered with a single word but would still be a real answer, and when it ends on a question she can answer in a sentence. It should leave out your own backstory, any second question stacked on the first, and anything that makes the reply feel like it needs a thoughtful response. Keep it light and let the question do the work.

If you send a follow up within a few hours of a one word reply, the message will read as continuing the same mood. If you wait until the next morning, it will read as a fresh start. For most casual threads, waiting until the next day for a second message is the right call, unless she sent something that clearly invited a quick response. Sending at 2am after a one word reply reads as more interest than you want to show, and it can get a short answer back for the wrong reasons.

If she does not answer your follow up, send nothing for a few days. One message after silence is fine, and it should be lighter than what came before, with no apology and no explanation for why you were away. If that also gets no reply, stop. A thread that dies twice in a row has told you what you need to know, and it is better to let it go cleanly than to keep sending lines into silence.