The Mercedarian Sisters, the female wing of the Order of Mercy. This illustration is a generic one and I had to use some conjecture. I used the the Mercedarian Sisters of the Blessed Sacrament as inspiration. They use a necklace as part of the habit, but I couldn't find any pics that gave me a good enough view to replicate them. When I figure out what they are I will update the illustration.
For some reason the Mercedarian Sisters I have come across use a modern habit, as opposed to the friars that still use a traditional habit.