Who is Mary from a famous nursery rhyme?

Mary, Mary, quite contrary,How does your garden grow?With silver bells, and cockleshells,And pretty maids all in a row.

1st line- Referring To Bloody Mary

2nd line- The garden is a cemetery

3rd line- Silver bells and cockleshells are instruments of torture

4th line- The 'pretty maids all in a row' are guillotines that are lined up in rows