Common fault with these. If the snib (small button-like thing) won’t move, there’s nothing she can do except call a locksmith. They will drill from the outside, release and replace. If it’s ground floor, they should try to climb through a window and do it from inside as it will save the cylinder.
You friend should take a video that shows it’s jammed and screenshot her phone’s call log to prove that she attempted to contact the landlord.
Expect to pay a total of £150-£200 or so to have this done tonight. It should all be recoverable from the landlord but if you have trouble with that, post on r/legaladviceuk
Make sure you get a full price over the phone from the locksmith and follow the advice in the sidebar to see how to find a good one. Easy to quote this from photos so don’t put up with any nonsense from people that tell you they have to wait until they are on site.
(I’ve assumed UK, judging by the your lock)