Westjet crews are generally very helpful with small kids and will go out of their way to help you if you ask, and sometimes even if you don't ask.

In my experience with Westjet, they do not have milk on board, so if you need to give your child milk, remember to buy some at Tim Horton's once you are past security (they sell 500 ml cartons).

If your child enjoys watching television, you might want to bring a pair of suitably sized headphones so that she can watch the live satellite TV (Treehouse is available on one of the channels).

Since your child is less than 2 years old, the crew may ask you to hold her during takeoff/landing, even though she has her own seat.

I travel often between YYZ and YWG with my 4 year old son and 2 1/2 year old twin daughters. Our experience on both AC and Westjet makes us prefer Westjet due to their helpful staff and no hassles with gate checking strollers etc. Last year AC implemented a short-lived policy of not gate checking any strollers larger than umbrella strollers - we chose not to fly on AC because of this until they removed the policy a few months later.