From the Govt website ….
If you are studying at degree level or above, you can stay for the full duration of your course, up to four years.
If your course is longer than four years, you can apply for a UK Visa Extension to finish your course.
If you are studying below degree, your Student Visa will allow you to stay for up to three years.
One route for staying in the UK beyond a course of study, is through switching to a Tier 2 Work Permit. You will require a specific offer of employment from a British company.
It may well be worth her while getting round to applying for a position well before the course finishes,
and the rule isn’t new about student visas, afaik they have always finished as the course finishes and the rule will certainly have been in place when she started her course … of course not every student visa may be issued to students who are actually studying and thts one of the reasons for enforcing rules more strongly even though though it hurts those who play by them more than those who ignore them