Why did the Voleth Meir appear in dreams of these people?

Question

In The Witcher, season 2, Voleth Meir or the deathless mother appeared in the dream of only three people, Francesca Findabair, Fringilla Vigo, and Yennefer of Vengerberg. Why did she appear in the dreams of only these three people?

Answer 1

Firstly, Voleth Meir has not been active the whole time since she was imprisoned all those years ago by the first witchers. She only awoke when Ciri screamed at Cintra and broke the Monolith.

Ciri: My scream woke Voleth Meir.

_{The Witcher, Season 2 Episode 8, "Family"}

We then know that she only appeared to these 3, who are all mages, when they were nearing a location that led them to her. She brought the 3 of them together through the shared dreams and they then discovered her within the temple.

Yennefer: It's Elder speech, but primitive. "Behold the mother of forests, the deathless mother, nesting in dreams." The rest is gibberish.

No. It's an incantation.

[...]

Voleth Meir: Turn your back to the forest.

She's calling us.

_{The Witcher, Season 2 Episode 2, "Kaer Morhen"}

From the above we can speculate that she only appears to these 3 because of who they are and because they have the ability to get to her. We also know that all 3 suffer with a great deal of pain which Voleth Meir can use to get powerful enough to escape.

Lastly, I'll note that just because she is only shown to appear to these three doesn't mean that she only appears to these three. It's just that they're the only three that we're following who she appears too. She's not exactly going to appear to a witcher or Ciri and give her presence away. No one else is really a main enough character that we follow who she would appear to except maybe Jasker.

Answer 2

Voleth Meir doesn't appear in canon, so it is hard to answer the question unless someone can find a quote by the director or such.

It has been noted that the character seems very much inspired by Slavic folk lore, where the witch Baba Yaga lives in a hut on legs. This witch is in some versions of the myth presented as three identical sisters, which could explain why the script writer decided to let three sorceresses get her visions.

A lot of the material of season 2 in the show is not canon. For example, in canon this is what actually happens during the Battle of Sodden Hill:

• Francesca is a member of the Brotherhood and fights against Nilfgaard at Sodden Hill. She remains loyal to the Brotherhood until later on in the story. She never gets pregnant nor have a romantic relation with Filavandrel.
• Fringilla fights for Nilfgaard like in the show, but not because she is a royal advisor but since it is her homeland - she's from somewhere around Toussaint.
• During the battle, Fringilla magically blinds Yennefer. Yennefer does not lose her powers though. Her sight is later restored.

So it wouldn't make much sense for any of the three sorceresses to make a deal with the witch like in the show.

Furthermore in canon, it is actually Triss who everyone think died and who get her named carved on the memorial as "Fourteenth of the Hill". In the show they switched this with Yennefer.