How can a girl trust someone she met online, despite his suspicious behavior, and what is the ruling of God regarding this person, and will she regain her right from him?

Familiarity between men and women is not permissible, even if for the purpose of marriage, due to the strife and corruption it leads to. It is obligatory to repent to Allah by ending the relationship with this young man and not preoccupying oneself with him, while fulfilling the conditions of repentance, learning the rulings of the religion, and strengthening one's connection with Allah. Among the things that help in this are associating with righteous women, listening to beneficial admonitions, and frequent remembrance (dhikr) and supplication (du'a).