In this context, it means that the potpourri was made by Mrs. Jevons using a recipe she'd created herself.
You could reword the sentence using the word follow, and it would retain the same meaning:
Potpourri was provided, made by Mrs. Jevons who followed her own recipe, to take away the smell.
From what I can tell, it's an unusual usage of the word "to", but it may have been chosen to help the sentence flow better, or to place emphases on the fact that it's her own recipe.
I believe the phrase "made to measure" uses the word "to" in a similar way.