Why do you think Félicité is hurt by people's jokes about Loulou?

Félicité is hurt by people's jokes about Loulou because she genuinely cares for the bird. It is another instance where her emotions are not taken seriously by the people around her. In this case, there may be some irony in it because her affection is so entirely given now to a bird instead of a person. However, her feeling is portrayed or described by the narrator ironically and it seems just as hurtful to Félicité that people disregard her feelings in this instance as in the others we've seen in the story, such as her love for Victor.