Describe how Vianne was a good mother. Use quotes from the text to support your answer.
One example is how Vianne is a positive role model for her daughter is by accepting everyone's beliefs. But I can't find a quote for this.
In describing Vianne as a good mother, it is a good idea to brainstorm some ideas before looking for quotes. I like what you have so far in labeling her as one who accepts everyone's beliefs. If I'm correctly understanding you, a better way to say this might be to simply call her "open-minded." This seems to maintain the same positive connotation, but doesn't present the arguable side that all accepting could also be translated to non-confrontational and weak (which she certainly isn't). Also, it isn't necessarily true that she actually accepts everyone's beliefs. If she did, she wouldn't be pushing to keep her chocolate shop open in a town which attempts to fully observe sacrifice during Lent.
Similar to your first idea and playing off the open-minded description, you could look at Vianne's general acceptance of all people, no matter who they are, where they come from, what they are hiding, nor how society feels about them. Even her enemy, the priest, is welcomed in her shop and spoken to with kindness.
When she meets Guillaume she hands him a box of treats and says, "They're your favorite kind...I know everyone's favorite. Trust me, this is yours." (p. 18)
When she meets Josephine, who has just shoplifted from her, she gives her a package similar to the one the woman has stolen and finishes with, "On the house, Josephine...It's all right. They're your favorites." (p. 20)
You could find several other quotes throughout the book to support the way Vianne builds relationships without judgment and with kindness. This certainly could be considered a key trait of good motherhood and role modeling.