Right then and there. While standing in front of her.

The "looking too keen" and waiting thing is a bunch of crap. Why?

1) if you're needy/clingy your behavior will soon be known, you're just masking it by playing the waiting game - all the while building her up in your head

2) contacting early is a good way to weed-out (or 'qualify') seeing as you want somebody responsive to your needs; better off knowing this off the get-go rather than some time later

3) if she has a secure style of attachment and you wait some time before texting (probably well beyond a few days) she'll likely have already written you off, and will be indifferent about it framing it as you playing games and she'll simply move onto the next

4) ensures you'll stay fresh in her mind and aren't afraid to take initiative

5) gives you the chance to see how interested she really is, if she's 'short fuse' she'll make things easy for you (as it SHOULD be), but if she's a long fuse and requires a lot of work you can decide to put your energies elsewhere

Op you should avoid texting fucking at 13.00.