Believe me! I feel ashamed of speaking about this but just with the intention of attaining purity and Islam I raise this question. Is it possible for girls to have sex with fingers? In this state, when does the Ghusl (Bathing) become compulsory? Can she do sex with fingers till she gets satisfaction?
If finger is inserted inside the vagina for the purpose of sex and excitement, and climax is reached, then Ghusl (Bathing) becomes compulsory. Therefore it is necessary to refrain from such impermissible course of action. Further, in these circumstances one should persuade the parents or other caretakers for marriage in a suitable way.
Allah knows best.