You can't guarantee it, zachary, just get to the check-in as early as possible so you are at the head of the queue - but check the easyjet website to see if your daughter is too old for "child boarding" as they board families with young children first. Otherwise we have never bothered with speedy boarding, in airports where you may have to use a bus for transport it just means you get on the bus first - and it's a gamble anyway. The other option is to sit across the aisle from her - I like an aisle seat and we often find that twos get in the window and next seat, leaving aisle seats free. If you are there early enough and head towards the back of the plane, there often seem to be more seats there than in the front (or vice versa if you are loading from the back).