Is it permissible to supplicate for marriage to a girl with whom there was a previous relationship, and to supplicate for her well-being during prayer while sending her religious messages after repentance and severing the relationship?

May Allah reward you both for severing the suspicious relationship. We advise you to continue on this path until Allah ordains for you a lawful marriage. It is permissible to supplicate that a certain woman becomes your wife, provided she is not already married. Likewise, it is permissible to supplicate for her guidance and protection during prayer or at other times.