Based on the below linked videos from Rachael's vigil, it seems more likely that her campsite in somewhere in the vicinity of the below marked map. I based this on 1. the video(s) show a fork off of Hernandez road to a dirt road named "Genesee Street" that leads to her campsite and has been blocked off by LE. 2. Based off multiple articles that were linked by others (please correct me if I am wrong), her campsite was described as being on a narrow dirt road alongside the Sacandaga river.
The general site marked on the below map seems to be the only area (that is visible on the available maps) that matches this criteria.
Video Links:
http://wnyt.com/news/vigil-for-missing-johnstown-woman/4185218/
http://cbs6albany.com/news/local/search-still-underway-for-rachael-mattice
What I also found interesting from the WNYT video was Rachael's aunt's interview in which she states that Rachael's friend CN was supposed to stay with Rachael at the campsite the weekend after Rachael went missing, and that Rachael's friend actually showed up to the campsite on Friday (the same day Rachael's father arrived at the campsite and reported Rachael missing). Could it be that Rachael's friend was the first to arrive and alerted Rachel's father when she realized that Rachael was not there? With so much little information being released about this case, it leads me to question some of the initial media reports.
Also useful in the WNYT video is the visual of the bridge area in which Rachael last texted her mother at 9:15(?) PM. Based off of the video, and google map images, a possible area for this text was the intersection of old state road 30 and county road 5, where there is a parking area.