What is the ruling on a fiancée staying with her fiancé under one roof and his leading her in prayer?

A suitor is a stranger to his fiancée until he marries her. Therefore, he is not permitted to speak with her or contact her except to the extent allowed by Islamic law. There is no harm in the suitor and his fiancée being under one roof or praying together, as long as it does not lead to temptation. However, all of this should be avoided if there is no need for it, and it is preferable to hasten the legal marriage contract and consummation.