How Long should i wait?

Here's the story: One of my friend's female buddies have been hanging with us for several months now, and i've been spending alot of time flirting with her (mutually). Anyways, the other day I visited her while she was at work, and it got really busy so I handed her my phone number to grab lunch later, and she seemed really excited. That was two days ago. Is she waiting out the 'three days' thing, making me wait, or something like that, or holding back because it's fathers day weekend? Does anyone have a similar experience like this? When is she going to call?