However rare they are in folktales. Cinderella is usually helped by her dead mother's grave, or an animal connected to it. Followed by not needing any help, followed by help from a magical being whose test she passed, followed by a magical being who wants her firstborn, followed by an assortment of beings of whom a fairy godmother is only one.
At least mine are willing to be -- ehem -- Fair Folk.
There are witches who turn women into sheep and have them killed so they can slip into their place in the family and be in a position to marry off their daughters to a prince. Or just jump at the chance to be a stepmother.
The heroine knows, of course, that the prince and oldest son talking about how the king set him and his brothers to finding brides is in the Frog Princess.
The trick is that it takes time for her to think about it, and the prince is speaking briskly, and doesn't have too much to say. She can't stand there and think all day.
And the Frog Princess is not one of those tales that everyone knows and will recognize with an allusion.
The heroine is telling a fairy tale, and I know she can't have the main character look for apples to cure the king. Or water to cure the king. Or a firebird which may or may not be needed to cure the king.
Well, not too far into the story, she knows all about the death of her uncle. Something about reviving him from the dead does not leave her room for ignorance, especially since they talk along the way. (Along with the fox.)