Source: Curse of Strahd as Madam Eva, uses same Stat Block in Page 233

Whatever or not Madam Katarina will appear in Æthercoil is up in the air. Of course, she’ll be closer to Esmerelda than Madam Eva there. Some of the NPCs in that setting are inspired by Disney movies.

To the general folk who know of her, she’s a beautiful Vistani fortune-teller (resembling Esmerelda from Disney’s Hunchback of Norte Dane) who roams through the Realms in her colorful wagon, lead only by her own wiles to where she’s needed the most. She seems to know as much about the Mists of Ravenloft than she knows, almost as much as she knows those she tells fortunes to.

She should know about Ravenloft. She’s known there as Madam Eva. That’s right, the very same crone that tells you the Fortune.

Eva is known to travel across many planes, using the Mists to planeswalk as is her privilege as a Vistani of Ravenloft. In the Realms, she could temporarily deactivate the pact she made with Mother Night (one of the few deities in the Ravenloft setting) and regain her youth. This reactivates when she returns to the Ravenloft plane, returning to Madam Eva.

Whenever there is a need for some random generation in a campaign or quest, I’ll have Katarina appear, do the reading, and then leave.