Property is a long-term investment, especially when the housing market is still depressed, although, of course, that's a good time to buy. However, being realistic, your mother may not have much time left. When she dies, the property will almost certainly have to be sold, especially if all savings have been converted to property so there is nothing liquid to pay inheritance tax (40%). There is no predicting when the market will improve.
Even if rental property is in good condition to begin with, it also involves quite a bit of maintenance and organisation. This can be handled by an agent but they do charge for every last thing they do on top of their commission. However, agents will also advertise the property, show viewers round it and do credit checks on potential tenants.
It's a tricky decision ChrisGollins with interest rates on savings in the doldrums. There is no easy solution. Good luck.