What should a female student do if she feels a moisture that invalidates ablution when wearing jeans, and she does not find time for ablution at school, while Dhuhr prayer time ends before she returns home?

If your feeling of discharge is merely a doubt, then nothing is required of you. However, if you are certain of its exit, then you must perform ablution for prayer. These secretions are pure, and there is no need to wash what has touched the body or clothes from them. It is not permissible to delay prayer beyond its time; rather, you should perform it within its prescribed time. If you are not permitted to perform ablution and are harmed by missing classes, then it is permissible for you to combine Dhuhr and Asr prayers by delaying Dhuhr (jam' ta'khir) due to need.