Is mum lying ?

Hello, 

My mother was diagnosed with stage 4 cancer 6 years ago, we have no relationship and so hadnt been around her or my sister to know the ins and outs of whats going on. Im unsure as to whether my sisters even attend mums apps. Latenlast year she telephoned my grandad saying she was in hospital with sepsis and that she wouldnt make it, it transpired she was only in hospital for a tooth extraction and had no sepsis at all. 

A few months ago I was told all treatment was going to be stopped as it wasnt working and the cancer had spread to brain, liver and bone marrow and she was only going to be receiving weekly blood transfusions. 

Last week when a relative saw her she was out shopping walking unaided, whereas before she was in a wheelchair, looking really well and planning on going back to work in a couple of months time. 

I have no idea what to believe, and where I dont have a relationship with my siblings I cant reach out and ask them because they are very much under my mothers control still. 

Please can anyone help because mentally im not doing great is she lying ? Is this normal ? 

Thank you