What to do about lump sum from endowment

Hi
Firstly thank you so much to those who gave advice about how to get UC contributions towards my sister’s ridiculously high service charges on her flat. UC have agreed to pay some towards this (nowhere near covers it but every little helps!).
Also I’m thinking ahead.
In about a year’s time she has an endowment which matures (was connected to mortgage but our mother paid her mortgage off years ago). Last time I looked I think the sum was about 18k so will bring her over the savings threshold.
However, she owes the management company 34k towards major works (I know - v depressing!) as a result of the crooked freeholder’s negligence for many years. This may be a bit reduced as the court appointed management company are suing the freeholder for his debts (he owns various flats in the block and hasn’t paid service charges for years). But it won’t be reduced by much such is the state of the buildings after years of neglect.
As her POA/appointee what shall I do? Does DWP “pause” benefits? The lump sum will literally be in her account for minutes until I switch it to pay off some of the debt with the management company. Or do I just do what I need to do and retain all documentation in case she has a review where they examine her bank accounts.
Just want to do the right thing but the idea of starting all over again trying to get her benefits sorted is pretty stressful (if they temporarily stop them). She’s on ESA and UC (LCWRA).
She’s in East Midlands.