What to say when she says that sounds fun but I usually plan my dates ahead

"That sounds fun" is a reaction to the idea. It is not an answer to the time, the place, or the question of whether she wants to meet you. Often she is interested and still deciding, or she likes that you have thought about it but is not sure the specifics suit her week. A short, pleasant reply with no question attached usually means she is waiting to see what you do with the opening.

Check the rest of the thread before you decide what it means. If she has been asking you questions, sending longer messages, and picking up threads, the soft reply is probably just texting style. If her messages have been getting shorter and she has stopped asking things back, the plan may be landing as too fixed, and you should loosen it.

The move is to keep the core of what you proposed while leaving one or two specifics for her to shape. Name the kind of thing you are doing and the general window, then ask which part she would prefer, or whether a different day suits her better. This gives her a real choice that costs her nothing to answer.

A good draft is short. It restates the idea in a sentence, offers one or two real options, and ends with an easy question about which works. Leave out the reservation time, the full address, and anything that sounds locked. The reply should make it obvious she can pick the day or the place, so the plan feels joint without you having to drop it entirely.

Give her a reasonable window before you follow up. Usually that means waiting until the next day, or until the following morning if it was late at night. A plan message sent at 11pm will get a response in the morning, and a follow-up sent an hour later reads as anxious.

If she does not answer, send one short nudge that gives her an easy out, something like a simple check that the window still suits her. If she still does not answer, let it go for now and do not send a third message. If she replies later with interest, pick it back up without mentioning the silence. If she never picks it up, the conversation has told you what you needed to know, and you can stop without making it a thing.