Unfortunately it's not fair but there's not much you can do about it.
It'll pass easily in Yr 11 but she's playing a risky game doing it in Year 12. A teacher could notice. Or she'll get burnt not being able to adapt in unseen questions. But it's not going to help you getting involved in trying to call her out unless you have absolute concrete evidence, which is almost impossible to have in these instances. Yr 11 has no bearing on Year 12, so it's not affecting you in the larger scheme of things (like it could in Year 12) and hurting her chance to improve her own English skill before Year 12.