What happened after the guests ate the wedding cake and why didn’t it affect Tita? Why and how was Tita punished for this?

The guests who have eaten the wedding cake are overcome with feelings of longing just as Nacha was when she tasted the icing. Everyone, even Mama Elena, begins crying and vomiting uncontrollably. Tita remains unaffected. Rosaura blames Tita for putting something into the cake and Tita receives a severe beating from Mama Elena who also believes Tita and Nacha conspired to ruin the wedding party.