I'm not sure why you find it so difficult to comprehend that people lie to get PIP. As I've said before, there are entire groups on social media dedicated to helping people claim when they aren't disabled.
If that's true then surely the government can easily find these groups and investigate anyone committing fraud.
She is a good liar. Again, as I've already said, ages gone to the lengths to get a wheelchair to keep in her house.
Good liar you say. So perhaps lying to you about her health issues - as in downplaying her health issues, or telling you it's physical health issues when it's actually mental illness.
Sadly due to disability discrimination, some disabled and ill people feel ashamed and downplay it. Such a shame society has made people feel they have to do that.
Separately as I posted yesterday. Yes probably a small minority of people "play the system". People commit crimes - all types of crime. So it's likely that the small minority who might be faking illness, if not doing that, would just do another crime instead.
Meanwhile the majority of claimants are genuine. Also, as I (and other posters) also pointed out yesterday, there's more people entitled to and in need of benefits who aren't claiming (and struggling as a result). That's been officially reported.