Is the questioner considered an apostate due to past actions and statements that occurred before and after puberty, such as thinking that angels are daughters of God, or making the sign of the cross, or saying "I am a disbeliever" without intending apostasy? And was her pronouncement of the Two Testimonies (Shahadatayn) and her prayers sufficient for her to remain in Islam?

What occurred before puberty is not taken into consideration, as the pen is lifted from the child. Disbelief does not occur merely by moving a cross, because that is not an act of worship to it. As for your statement, "I am a disbeliever," your pronouncement of the two Shahadas and your prayers nullify it. Performing ghusl and uttering the two Shahadas with the intention of entering Islam after that are manifestations of waswasah (whispers from Satan) that must be struggled against. You must turn away from these waswasah and seek Allah's help against them. Seek refuge in Allah and say "I believe in Allah and His messengers" when they occur.