I wouldn't want one in there after 7 inches either, but in my experience, female GTs take a long time to get to that size, so if you got one while she was young, the 35G would last a while. I had one that lived in a 40G for nearly 2 years, good water changes, good food, good filtration, and it took the full 2 years to get to 8". Some may grow a bit faster, but usually not a whole lot. Males as you probably know will get a fair amount larger (10+ inches not that uncommon) and get there quicker too. Your call, but I would say that it will work for quite some time for a female.