Talking with the fiancée
If a girl has been betrothed to a boy and an engagement ceremony has been done, then the girl and the boy freely talk with each other without any reservations. They don’t find any problem in roaming with each other.
If a match has been made with any girl then the Shariah treats this as a promise of marriage. They don’t become husband and wife after the engagement. Only an engagement doesn’t obligate marriage as long as offer and acceptance of marriage is not done in the presence of 2 witnesses as required by the Shariah.
Thus, the guy does not become the husband of the girl only because of the engagement nor does the girl become the wife of the guy. On the contrary, both of them are still unrelated strangers (non-Mahram) to each other until their marriage takes place. Thus, freely talking with or meeting the fiancée before the marriage is impermissible.
As given in Durre Mukhtaar, Vol. 5, Pg. No. 260: