There was never any dialogue that said she was in her 30s in DAO. In fact, the age range they gave her VA was that she was around 26 in Origins. So that would mean she is in her mid to late 30s in Inquisition.
Hum link please? in the dialogue she talk with Wynne if I am not mistaken that she is much older than she looks.
If you are right than maybe she has the same age as Celene because Celene is born on 9:6 and is Empress at 9:20, this means she was 14 and if Justinia V is made the Divine on 9:34 this means it is after the blight.
Now from TIM we know that Celene knew of Majory and Leliana, so that puts the Leliana DLC between 9:20 and 9: 30(the Bligh during DA:O), I am going to assume here that she has the same age as Celene, so the Leliana DLC would be maybe 9:27? But that would put her at her yearly 20s with 24 years old, which makes her remark with Wynne strange.
After some reflecting, maybe she was born on 9:02, which makes her 38 at 9:40. I still think that maybe Leliana is 40 years old.