That is a good point. Probably, it is a title. There is "Mother", "Father" and "Brother." I am a Protestant, and I don't know how Catholics view the issue. I have never regarded the religious name as a legal name. This lady was known by her middle name of Rose before she became a Sister, so she doesn't really fit.
In my experience indexing deaths, the deceased in this case would be listed in the newspaper as
MARCHANT, Dorothy Rose (Rose) (Sister Walburga); she hadn't lost her original name. I feel like transferring the Profile to Pauline and l.etting her sort it out, but she is less familiar with Wikitree.