hi looking at your pictures i would say 3 weeks or so. she will be real close by then. i know this is your first grow and you want to get the harvest you worked for. by waiting the 3 weeks you will start seeing that the buds are changing, by the 3 weeks you will also notice your buds get a little bigger.
the true wat to know when she is ready is by checking the trichomes under a jeweler's loop. the trichomes are the little tiny balloons that swell up with thc, they start swelling clear then to a milky cloudy to an amber. when these are milky they are ready but the milky will be more a head high, while getting the amber at 20-30% amber then the plant has the maximum thc in the plant and the buzz is more a couch lock buzz or heavy. so harvest when you think will suit your needs. congrats on your soon to be harvest you did great