Can you claim benefits when you quit a job?

Does anyone know? I have a dear SIL aged 60 who, thanks to this iniquitous moving of pension age, cannot receive her (only) state pension for years yet so has to keep working. She works for a small firm and is being taken advantage of/bullied. She is applying for jobs but has not yet been successful.
So. . . . . If she quits this job because conditions are becoming unbearable will she be able to claim benefits does anyone know? Or where we can find out?