If she has filled the application form and paid the registration fees, she cannot change the exam course details until the website opens a correction window.

Do check the official website for the correction window and there you can add/ change course of exam selected previously.

For more information , go through the link:

https://engineering.careers360.com/articles/jee-main-application-form-correction#:~:text=Step%201%2D%20Open%20JEE%20Main,for%20JEE%20Main%20correction%20window.

if she already apply for session 2 then wait because NTA definitely open correction window .I think its open now you can check or wait.

stay up to date

thank you

all the best