As a QQ enjoyer myself, I do recommend using her ultimate when you get 4 of a kind. You get a huge damage buff while you're holding onto 4 identical jades and it'll apply to your ultimate, but only if you use it before using your auto, which means you "waste" the free 4 of a kind the ult gives you, but you generally don't want that anyways since you'll be missing out on the damage bonus you get from rolling with your skill.
I pulled, saw it light up so skipped when I saw the 5 stars... only to get welt... got her a bit afterwards, and her E1 too... and her lightcone in my first 10 pull coming of a 150 streak before for Dan Heng's... so ehehehe....