Valanne,
First of all, sorry I made a mistake about the hospital. I had a senior moment and read Dave's answer of Gemeral Cemetery as General Infirmary
The GRO index is a free site run by the general registry office and provides birth and death details which cannot be found elsewhere.
That facts remains the same. Whoever reported the death said she was 40 and whoever had her buried said she was 42.
The certificate would tell you where she died and who reported it.
When doing family research it is sometimes necessary to buy certificates to confirm some facts which cannot be confirmed any other way.
Regards, Dave
Edit: in this case the info about her age given on the death cert is also on Free BMD