All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
A girl at that age may have reached maturity and accordingly became competent for religious obligations. Please refer to Fatwa 83431 about the signs of reaching maturity.
If she has reached maturity and became competent for religious obligations, then she is responsible for her actions. Hence, it is impermissible for her to watch this animated movie. If she can leave the room, then she is obliged to do so; otherwise, she may stay without watching it. If she watches it, then she bears a sin for that. This is of course if she has reached maturity. If she has not reached puberty yet, then she bears no sin. The Prophet, sallallaahu ‘alayhi wa sallam, said: "The pen has been lifted from three (i.e. they shall not be held accountable for their actions); the child until he reaches puberty, the sleeping person until he wakes up, and the insane person until he regains sanity." [Ahmad and Abu Daawood]
As far as you are concerned, in principle you bear no sin for that. However, it is dangerous to send one's children to such schools which teach curricula that may corrupt them. Verily, you may bear sin for being lax and indifferent in this regard. Please refer to Fataawa 203785 and 81846.