To me still looks smaller than 4" ??? Could be just the pattern's ? Are you measuring the head and tail too. If so turtles only go by the shell !
http://www.redearslider.com/anatomy.html I use a caliper easier !
Sure you like the gravel but it's small and turtles test everything with there mouth. Before you have a big vet bill from her eating some and getting a blockage you may want to reconsider. Bare bottom works and would be easier to clean. Sand is small , if eaten does not cause blockage. Large river rocks are just to large to eat , looks great but harder to clean between them.
Unless she's very comfortable with you it's hard for most to check the youwho.
Piggley says thank for the photos , he says girl too !