Well well well.. we see Ellie is a fast mover. Some were a bit struck by this. She certainly finds him attractive and has expressed interest before. She initially asked David for a date when she worked fast food. She was rejected, but met David again outside the Lovecon, where she promptly stared at his ass. She doesn't want to work and hang with Quinn all the time, now, come on! She needs to use his dictionary. This was also foreshadowed in the comic titled Warm Ways. The lyrics heavily imply what would happen 'that night.' (and you may wanna scroll down the page for more info on that.)
Also as seen with Cinnamon, Juniper, and Anise.. being a fast-mover runs in the family. Buckinghams are the aggressors. I will miss Friday this week. Moving to Texas first week of June, and my do-list is mounting bad. Be back Tuesday.