In Words of Radiance, chapter 55, after Shallan hugs Wit (aka Hoid), Adolin jealously tells Wit:
Stick to women your own age.
To which Wit cryptically replies:
Well, that might be a little harder. I think there's only one of those around these parts, and she and I never did get along.
Are there any hints as to whom he might be referring to?
Hoid is said to have been at the shattering of Adonalsium (this is obviously not said in the books where precious few know that event, but has been confirmed by the author to various fans, and is backed up by the fact that he knows most of the Shardholders by their original names). That event was millenia ago.
So basically, the only woman his age that would be around would be a Shardholder holding one of the god-powers from that event. Which basically means he's probably referring to the bearer of Cultivation, whose real name I don't believe is known at this point, but who is believed to be female, and is anyway the only Shardholder that isn't either dead or utterly evil in the area.
Duchess Khrissalla, better known as Khriss, is a female worldhopper originally from the country of Elis on the Darkside of the shardworld Taldain.
coppermind
In Mistborn: Secret History, it is established that Khriss and Hoid (called The Drifter) don't really get along well.
“Someone destroyed the gateway in,” Nazh noted. “Someone incredibly foolhardy. Brash. Stupid. Didn’t—”
“You’re overselling it,” Kelsier said. “The Drifter told me what I did.” “The . . . who?” Khriss asked.
“Fellow with white hair,” Kelsier said. “Lanky, with a sharp nose and—”
“Damn,” Khriss said. “Did he get to the Well of Ascension?”
“Stole something there,” Kelsier said. “A bit of metal.”
“Damn,” Khriss said, looking at her servant. “We need to go. I’m sorry, Survivor.”
Mistborn: Secret History - Part 3: Spirit - Chapter 2
Khriss is also the in-universe author of Ars Arcanum, which mean she has been to/is on Roshar, and WoB has establish that she is a more knowledge worldhopper than Hoid.
