RGS takes on points, not distance, so it is possible, and girls do come from Maidstone (I think the bus route is convenient). Before the PAN was increased, the cut-off mark was about 8-10 above the pass mark, not sure about last year.
Fort Pitt - almost certainly not possible due to distance and reduced PAN.
Rainham Mark - think it takes on points, but possibly not practical due to distance. It's not convenient for us, so I'm not an expert on it I'm afraid.
Chatham Girls - tends to have availability, so definitely possible, although the journey might be impractical.
Good luck to your DD, mine is aiming for RGS this year