Thank you guys for the replies! I have wondered if it migth be her age too but her voice sounded too mature for me to really consider that option. Come to think of it, Amiro calls Saheila a child too but then again I believed that was some sort of elvish figure of speech. (I'm so used to the shorter dragonage elves that I'm having trouble with the divinity elves
I guess I'll be headcanoning Sebille to be as tall as Saheila)