What should a girl who has committed fornication with more than one person do, after repenting, for her sins to be forgiven, and does Hajj expiate all sins, including fornication?

What the girl did is ugly, but her remorse and fear of God's punishment are a good start for repentance, and she must resolve not to return to it. Repentance expiates sins, and one who repents of a sin is like one who has no sin. Hajj alone does not expiate sins, but repentance combined with Hajj is more likely to expiate sins.