Is it permissible to mix genders in study and work in hospitals, while fearing its effect on one's religion and heart, given the necessity for a woman to secure herself financially?

The widespread mixing in universities between male and female students is an objectionable matter that causes many problems and temptations, and opens the doors to corruption. However, if it is not possible for you to study at a non-mixed university, then there is no blame upon you for studying at a mixed university, provided you adhere to the Shariah controls.