One thing I forgot to mention.
The old woman's black clothes are not necessarily mourning garb. They could be but it wouldn't be true in all cases.
If a woman's husband died when she was older, she might wear black for a longer time. If she was young, she might only wear black for a short time.
Queen Victoria wore black for the rest of her life after Prince Albert died. Many others followed her and it did become tradition in some circles so it's not out of the question.