In the first season of Penny Dreadful, we see that Vanessa Ives has grown up next door to sir Malcolm and his family. In the second season, we learn that she has been an apprentice to a "day walker" for some time. In the third season, we see in flashbacks that she spend some time in the Banning Clinic.
How do all of these fit together? For how long was she institutionalised, and how long was she an apprentice?
From her headstone, visible in the final episode, we know that she was born in 1860 and died in 1892.
This means that she was 31 or 32 at the conclusion of the third season.