that being said, if the casting would be for VII, she would be way to young unless Ahsoka's race ages slowly
The Togruta's average life expectancy is 94 according to Wookieepedia, which is above real-world early-21st-century human life expectancy, but a bit below the life expectancy of Star Wars
Ahsoka was born c. 36 BBY (i.e. before the events of the original movie), and Return of the Jedi
takes place in 4 ABY. So if Episode VII is c. 30 years after ROTJ, then Ahsoka would be c. 70 at that time.