Did Cady in Mean Girls experience any stressors?

Yes, Cady in Mean Girls experienced many stressors. Cady, portrayed by Lindsey Lohan, immediately experiences one of the biggest stress events—she moves from Africa to America and has to enroll in school. This in and of itself leads to many stressful situations such as finding friends, adapting to new customs, and more.
Another big stressor she experiences is relationship drama. She is interested in a boy at school, but that boy is "off-limits" because her friend Regina wants to date him. She is also caught between two friend groups, one of whom uses her to enact revenge on the other, which includes popular girls like Regina.
A final stressor is the school environment itself. She is attempting to get good grades, maintain a social life, and engage in extracurricular activities like the math team. This is taxing on her time, and it becomes even worse when she is punished for her deeds against the popular girls and has less time on her hands.