As the lady has no current partner, Pension Credit almost certainly comes into play, irrespective of what her actual State Pension entitlement is.
Assuming that she's got no other income (e.g. from shares etc, as it's her
total income that's relevant for State Pension purposes), it doesn't matter whether she gets £50 per week, £100 per week or £150 per week as her State Pension because, whatever that amount, Pension Credit will top it up to a total of £177.10 per week.
However she won't get Pension Credit unless she actually APPLIES for it. (It can't be automatic because the people who pay her State Pension have no knowledge of whether or not she has any additional income from shares, etc.). So, if the lady isn't already in receipt of Pension Credit, she needs to apply a.s.a.p!
https://www.gov.uk/pension-credit
Anyone in receipt of Pension Credit is entitled to a reduction in their Council Tax. (In many cases that can be a 100% reduction, totally wiping out her Council Tax bill). It also comes with additional benefits, such as a free TV licence for anyone aged 75 or over and help with heating costs.