ESA over £16000

Hi - I'm looking for some advice.

My mum has MS and has done for around 30 years or so. She claims higher level PIP and ESA with the additional components for being severely disabled. She has claimed these (and the previous DLA/Income Support) for years and years as she is profoundly disabled and hasn't been able to works for a long long time.

Recently, her savings have crept above the 16000 threshold (various reasons - not going out as much, not shopping as much, stuck in the house - as well as us stupidly getting her shopping for her and not getting money back etc etc). Shes always been close to the £16000 but not over it. Shes around at around £17000.

Annoyingly, she has now been asked to supply her yearly statements for DWP to review - obviously I know you cannot be above £16000 HOWEVER I'm confused as to how it all works. I know some is based on contribution based (will my mum qualify for this if shes been on benefits for so long?), Can she still claim the disabled part of the money is shes over?
Obviously we will take some money from her account and take it under the 16000 mark but they want months of statements so will see it has crept up at times. Will she lose everything? She has only managed to surpass the threshold due to her being very poorly lately so savings will no doubt go down again anyway!

Any help appreciated.