It is usually said that after an intercourse, a female vaginal membrane got broken and hence the blood comes out of vagina, it is also said that this blood comes out only for the first time of intercourse. This blood is the only proof with a girl that she's a virgin.

Please explain me either all these facts are right. If a girl had a sex before marriage and lost her virginity and by the time she realized that intercourse is not the right thing before marriage and abstains from doing it again, can she be develop again? What are the ways of recovering. How can a girl protect herself if she doesn't marry a guy she intercoursed, but someone else?