My sister studies in school with boys. When she wants to pray in a special place for women she does not put off the (Niqab), so the (Jabha) of face didn't touch the earth and she say that she can't take it off because someone might see her from the ceiling.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Your sister’s prayer with Niqab on her face (face cover) in the presence of non-Mahram men, or when she suspects that they may see her, is valid. Some contemporary scholars are even of the view that covering the face during the prayer becomes obligatory when there are non-Mahram men. Shaykh Ibn Uthaymeen also holds the same opinion.

Moreover, it is not a condition that the forehead touches the ground during prostration to make the prayer valid.

The Prophet sometimes performed the prayer on a mat and the companions performed their prayers on their clothes due to scorching heat as reported in Saheeh Al-Bukhari.

For this narration, the majority of the Muslim scholars permitted prostrating over a cloth, a turban, or a mat. The same ruling applies to the face of the woman.

As long as she is studying in a co-education institute, we warn her of the following matters.

If she can get her education in any girls' institute, then she should leave that mixed school and join the girls' institute. If there is no institute providing separate education for girls and she needs to continue her study, then she should take all precautions to avoid committing forbidden acts.

She should try to apply the following:

A) Her attendance should be limited only to lectures.

B) She should go out of her house wearing her complete Hijab, and not wearing any perfume.

C) She should also avoid sitting beside men, socializing with them, or talking to them.

Allah knows best.