What is the most likely reason that Mathilde picks the diamond necklace to borrow from Madame Forestier?

Answer 1

The most likely reason that Mathilde picks the diamond necklace to borrow from Madame Forestier is because she believes that wearing such a luxurious and expensive piece of jewelry will make her look affluent and high-class at the fancy event she is attending. Mathilde dreams of being part of the upper class and desires to appear wealthy, and she thinks that by wearing the necklace, she can achieve that appearance.