Reference: al-Muqarrab li-Ahkaam al-Janaa.iz – Question 140, Pages 120-121
Question: Her husband has died and she is required to complete the period of mourning. [Considering] she is a student at school, is it permissible for her to continue her studies or not?
Response: It is obligatory for the wife whose husband has died to complete the mourning period in the marital home and no where else for the duration of four months and ten days. [Additionally] she must refrain from that which beautifies her from perfume, eyeliner and eye-catching clothes and beautifying herself in general and all that attracts others to look at her.
[Also], it is permissible for her to go out during the day for necessities, and based upon this, it is permissible for her to continue going to school for the need of seeking knowledge and understanding issues, making sure that she refrains from that which is obligatory upon the one in her mourning period from that which leads men astray and [thereby] inviting marriage proposals.
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet Muhammad (sal-Allaahu `alayhi wa sallam) and his family and his companions.