Hi Laoisa,
You seem to be looking at 3 options. 1 An Investment property. 2 The market through a broker. 3 A post office saving scheme.
Let me give you some pros and cons for each.
1 An Investment property
This is long term, don't even consider it unless you are happy to have the money tied up in the property for at least 5 years.
Property investment is a type of business and you need to know what you are at. You have asked about hassle, I think hassle is a bad way to describe it, I would say it is work and sometimes hard work.
You can lessen the work by using an agent or renting to the council, but at the end of the day you are still the landlord. If there are problems, and there will be, the buck stops with you.
The advantage is, in my opinion, that property offers the best return.
2 The market through a broker
If you don't know what you are doing you are putting your trust in a broker. For me this is unacceptable. I am sure there are many fine brokers out there, but I am also aware of people being put into totally unsuitable investments by large and ostensibly respectable brokers. These all involve the customer taking on much more risk than they should.
Done well this may give a good reward, but done badly you could loose your money.
3 A post office saving scheme.
The returns are low.
There is no hassle, no work or knowledge required.
There is as near as it is possible to get no risk.
The reason your mother needs to make an investment is because she received an inheritance, I don't think that is a good reason to become a landlord, or even a stock market investor. In my opinion, go to the PO.
If you accept that idea, you may get more advice on here as to exactly which PO scheme, or Prize Bonds may best suit, but they are all more similar to each other than options 1 and 2 above.