Possible Clues:

• A diplomatic representative of the Pope
• Messenger's Greek letter with bent coin
• Ambassador, one in care of sister at first
• A religious lady - one in company representing the Roman Church
• From the good sister one gets a hundred and ten by way of a message
• Sister caught with one old ambassador
• For the Church she starts to make a messenger of him
• Papal diplomat
• How 20 down might start to be a representative
• She starts to be in papal service