The constraint is always raw material. She has no shortage of ideas or time in which to put them into practice. Hence, she is most avaricious in acquiring hearts whenever an opportunity presents itself. Having a stockpile means she need waste as little time as possible.
The Yew Queen then offers quite extensive, organized, actually helpful advice - rather unlike September's mostly intuition-based ramblings.
Her information should be enough for Shade to stop sleeping, assuming she cares about doing that, and heal most simple injuries. Endurance and speed are harder to summarize, more about sustained wanting to keep going, and endurance especially can be finicky to mess with. Still, if you can get sleeplessness and flight, those both synergize well with the required mindset.
That is helpful. Shade doesn't seem to be having much trouble with the wanting to keep going mindset.
"Why are being so helpful?"
"You're my ally, now. It's good, to help allies. Besides, I want to see you excel - you're already powerful, even with just fledgling potential. If you stay Heartful? Within a century the world will tremble at your coming."
"You're too nice for someone who was trying to kill me earlier in the day."
She laughs. "I wouldn't have actually killed you, not after you stood up to me, and especially not after your display of talent! And I likely would not have killed you, even if you had fled - I rarely kill the Heartful."
"There's potential there the Heartless don't really have. Little webs of passion and caring - a Heartless would hardly blink, except to be miffed I stole a fun toy, were I to kill their whole family."
"I'm playing a long game, somewhat. I would like to see the Heartful thrive, in a way they can't under the Heartless's dominion. I want to see their vibrancy spread - right now, if I wiped out a tribe or a village of them, the ripples are tiny."
"People are interesting in general! But maybe I can find you a selection of entertaining people to hunt, hm?"
She laughs. "I don't think hunting books is typical, but I'll see what I can scrounge up."
She hums, and redirects the conversation back to magic lessons, this time winding over towards divination - it's hard while you're in motion, and most need some kind of focus, like a pool of still water, but far-viewing is definitely possible, and it's rumored that future-viewing is, too...
Shade does not quite have the same talent for this sort of thing, but her stubborn attitude still prevails.
"We won't be able to go after your quarry directly," the Yew Queen comments. "But it is good to have somewhere to ride, when we set out tomorrow. There's a divination trick, that will give us a heading towards someone who might know something."