Am I overthinking or is this an actual red flag?

I have started dating again and I have a history of choosing emotionally unavailable people. I am determined that my next relationship feels secure and safe. However, I am aware that in part comes from me managing my anxiety and reactivity (I have adhd and anxiety which impacts my relationships).

I went on a really good first date with this girl and I was doing my best to not get too excited (just a first date). I wanted to schedule a second and she mentioned an activity we could do. It’s now been over a day without a response from her. It’s perfectly understandable that people get busy but I really don’t want to end up in another relationship with someone who is not communicative or invested. I feel like even if she does respond this is a red flag for how interested she is.

I guess my question is, if you were genuinely interested in dating someone, would you leave it that long to respond about a second date? This is the first person I’ve gone on a date with that I’ve liked since my ex and I broke up. I don’t wanna overreact but I just can’t date another person who keeps me hanging