All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The prayer is the most important pillar of Islam after the Shahaadah [the two testimonies of faith]. It is the prayer that distinguishes Islam from disbelief. Performing prayers is a sign of faith, and not performing it is a sign of disbelief and hypocrisy. Indeed Allaah warned those who neglect it or give it up. Allaah Says (interpretation of meaning): {Then, there has succeeded them a posterity who have given up the prayers [i.e. made their prayers to be lost, either by not offering them or by not offering them perfectly or by not offering them in their proper fixed times, etc.] and have followed lusts. So they will be thrown in Hell, except those who repent...}[19:59-60]. Allaah also says (interpretation of meaning): {So woe unto those performers of prayers (hypocrites), those who delay their prayer from their stated fixed times}[107:4-5]. The Prophet said: "The first thing a person will be held accountable for on the Day of Judgment is his prayers. If his prayers are correct (accepted) he/she will be successful, but if his/her prayers are not accepted, he/she will be a loser." [Tirmithi and others]. The Prophet also said: "Between a man and disbelief is abandoning the prayer (obligatory prayers)." [Muslim]. Therefore, dear sister, you have to observe the prayers and perform them at their fixed times. Allaah says (interpretation of meaning): {Verily, the prayer is enjoined on the believers at fixed hours.}[4:103]. Not performing prayers takes the person out of the fold of Islam, and delaying them from their fixed times is a sign of hypocrisy; so you have to be careful. In the life of a true believer, studying at the university or working is not more important than prayers, to the extent of being a cause for delaying them. A Muslim lives and dies for the sake of Allaah, and strives to save himself/herself from Hellfire. He/she should not have as a priority anything above the obedience of Allaah and His Prophet . You have to know that on the Day of Judgement Allaah may not ask you about your work or study, but He will ask you about your prayers. So you have to be very, very careful not to abandon the prayers or neglecting and delaying them from their fixed times. For more details and benefit, please refer to Fataawa: 88376, 87587, 84403 and 88378.
Allaah knows best.