Will God forgive a girl who cursed the Divine Being, religion, and the Prophet when she was 11 years old, and was ignorant of the حرمة (sanctity/prohibition) of her action?

Swearing at Allah is disbelief (kufr) and apostasy from Islam. However, it does not mean that the door to repentance is closed. Allah's mercy is vast, and He accepts sincere repentance, no matter how great the sins. The one who repents from a sin is like one who has no sin. So, trust in Allah's forgiveness, strive in acts of obedience, and do not let sin cause you to despair of Allah's mercy.