What is Mathilde most likely thinking and feeling when she hears Madame Forestier's confession?

When Mathilde hears Madame Forestier's confession about the necklace being a fake, she is likely overwhelmed with shock and disbelief. This revelation likely brings a mix of relief and despair; she realizes that her years of hardship and sacrifice were in vain for something that was not real. Mathilde may also feel a profound sense of regret for her vanity and the pride that led her to borrow the necklace in the first place. Ultimately, this moment forces her to confront the harsh realities of her life choices.