Yeah cant really see her gravid spot at all.
I have three Guppys all pregnant and not sure how long they are gone, though one has a REALLY black gravid spot and has had for nearly a week now.
After all the research i done online (hours!) it seems no one can really tell how far gone other owners guppys are gone without seeing their difference in behaviour stuff out of the norm etc. I would just keep a close eye on her and see what happens!
Sorry this hasn't helped much i know you wanted me to say "tomorrow" or something. In all honesty and with that picture i dont think anyone is going to give you an accurate answer.