Some children go through homosexual experimentation phases but eventually consider themselves heterosexual. Some children are the opposite.
Also, some children will experiment with homosexual relationships and eventually consider themselves homosexual. Some are, again, the opposite.
What a person defines as their sexual orientation when they are 10 is far from definite as to how they will consider themselves when they are 17. However, I would consider it a good indication, so I hope you are ok in case it does turn out she is bisexual or lesbian.
If your parents are not OK, it may be better not to tell them, or maybe she wants to tell them and see their reaction. Either way it is her decision to make. I personally would advise her not to inform her parents until absolutely necessary. Older people are set in their ways. It is not their fault they usually oppose homosexuals, they were just raised that way. It is very difficult for people to change their beliefs, as hard as that may be to accept. I personally would keep the secret from my parents if I were her. WHy make them unhappy? But that again is her decision, not ours.