IR ESA and CB ESA and impact of a company pension

I am trying to help a friend who is currently receiving IR ESA (support group and Severe Disability Premium) and DLA (Higher rate care and lower rate mobility).
She has received a letter from her former employer informing her she is entitled to a pension when she reaches 60 in July, £5200 per year, approx. £100 per month and a lump sum of £30,000.
I want to help her understand the impact the pension will have on her benefits. Although I know her DLA will be unaffected I cannot find any clear information about ESA.
Obviously the lump sum will rule out all means-tested benefits like IR ESA. But am I right in thinking she may be entitled to CB ESA instead? She hasn’t worked/paid NI contributions since she left her job due to illness/MS in the late 1990s. If she is entitled to this, how long would it be paid for? Is money deducted because she has the pension? It is impossible to find clear information anywhere about CB ESA and people with long-term illness disability.
If she spends the lump sum (she wants to use it along with the proceeds from her flat to buy a housing association bungalow) would she go back to IR ESA?
Finally, if she were to defer the pension for a couple of years would the DWP treat her as though she was receiving it. It is a Defined Benefit/final salary type pension. I can find clear information that suggests people can leave Defined Contribution pension pots untouched until they reach Pension Credit age without losing their means-tested benefits but absolutely nothing about final salary pensions.
I hope someone can advise or help.