May I respectfully suggest you are approaching this the wrong way round? You are starting with an end product, without determining whether or not it is appropriate.
The first thing to consider is how the money is to be used. Is it to provide income to supplement the state pension? And if so how much is needed a month/year? You would need to factor inflation into this as well, to maintain its buying power.
Next, you need to consider how much risk can be taken on any part of this sum. Can your relative accept any of it fluctuating in value in order to generate higher returns? Given her age and the fact that she only has one source of income, the answer may well be "no" - but the question still needs to be asked.
An income bond may be suitable, but remember the capital value remains static if all you do is take the income arising from it. That means it is decreasing in real terms – once inflation is taken into account.
Also, it is normally accepted that capital would be withdrawn over time to generate the required extra income. Obviously, you don't want that to happen too quickly with the risk that your relative's money would run out too fast. A financial planner would be able to estimate the return required on the money to ensure it lasts, based on reasonable assumptions about life expectancy, income required and inflation.
I appreciate this may seem more complicated than you perhaps envisaged, but at least by taking into account all the circumstances and requirements your relative should end up with something that is most appropriate.