She used to laugh at my jokes now gives short answers

Her shift didn't start when she stopped laughing. It started earlier. Maybe you went two days without texting. Maybe she brought up something and you deflected with humor instead of actually listening. Maybe the conversation had no direction and petered out, so now she's in a low-investment headspace.

Short answers after good jokes don't happen by accident. She's signaling that the momentum or the dynamic or your attention already died. The joke was just the moment you both noticed it. When you reply, you're not trying to make her laugh again. You're trying to restart whatever was actually working before the jokes stopped landing.

Your reply needs to do two jobs. First, drop the humor. You don't need to be unfunny or boring, just stop performing. Second, give her a reason to write more than four words back. This means asking about something she actually cares about, referencing something from earlier conversations that shows you listened, or saying something that requires a real answer instead of a reaction.

Don't announce the subject change. Just pivot naturally to something with stakes. A question about a goal she mentioned. Something that relates to her world, not your dynamic. This works because it resets the entire tone. You're not trying to get her to laugh at you again. You're trying to get her to think about you again.

Send one message that does the work above, then stop. Don't follow up. Don't 'just checking in'. Don't send a softer version of the same message. Give her two days minimum to reply. If she doesn't, the situation is already over and another message won't change it.

If she does reply, even briefly, that's a restart. You can then build back up by continuing to ask questions that let her talk about things she cares about. If three days pass with no reply to a solid message, move on. The short answers weren't the problem. They were just the sign that she'd already checked out.