Higher mobility DLA & ESA

Hi

I have been trying to help my mum with her benefits and getting in a bit of a mess! I have managed to work out that she receives ESA/SG and also DLA for mobility only. My mum was assessed 5 years ago and hasn't heard anything since, I'm not sure who sent for the assessment but I know that she was originally receiving Incapacity Benefit which was changed to ESA.

Is this right that someone can only receive the mobility part for DLA? She receives the higher allowance too, I am a bit confused as to why she only gets that and not the living part?

Any help you could give would be very much appreciated.

Thank You