I don't dislike her background so much as I find it weird.
There's a story here that I think needs to be elaborated on or they should have made a new character. I have no problem with an elven slave becoming a Grey Warden. That doesn't suspend my suspension of disbelief. The Grey Wardens draw from all the peoples of the world. I don't mind her being Alistair's mother TOO MUCH. To be honest, I do because Fiona makes Alisatir's mother "special" when she was SPECIAL because she was a maidservant. This is like Superman should date Wonder Woman because Lois Lane isn't a superhero.
Stupid.
I don't even mind her not going through the Calling. Albeit, this is GROUNDBREAKING.
The Wardens would want her studied head-to-toe.
However, HOW THE **** did she go from being a Grey Warden for a couple of decades to leader of the entire Circles?
This is a pretty big promotion for a person who wasn't shown to be THAT capable of a mage and doesn't have any networking capacity for decades.
If it's because she's 20th level, then that's at least an answer but I thought that was a game extrapolation.