She obviously knew she could trust you more than an unknown locksmith. However, it shows that some old people keep large quantities of cash around their houses, and these stories unfortunately make all older folk a good bet for house robberies.
When I started seeing my current lady friend, then aged about 62, she used to set aside a few pounds from her pension each week for utility bills, and hide it in a plastic rubbish bag in her kitchen. It took a bit of persuasion, but soon she had a current account and an ISA, (she had a part time job then) and learned to write cheques.