She needs longer nights and shorter days to start the flowering process.
This usually happens around the dark nights of the New Moon phase at about this time of year.
I would not be surprised if she starts flowering by the end of the month, but she probably wont finish until late October.
If she is near bright outdoor lights over night or even porch lights, these can also prevent flowering.
I see she is by your back door and under a down light, even going outside and switching the light on can delay flowering.
She needs uninterupted darkness to initiate flowering.