In regards to a child's rights in Florida...

This to me is an unusual & sad one...I listen to a 8 yr. old girl tell her Grandmother that she is going to move away from home when she turns 12...She somewhere got the idea that at that age it would be legal for her to do so? She says she is not sure where she will go but she does not like her adoptive mother & her boyfriend who allegedly show no love or concern for her...She says she can not stand to live in a cigarette smoke filled house...That alone is a good enough reason to me for a child to have the right to live in an environmentally healthy atmosphere so again I am inquiring in the state of Florida to see at what age a child can make such important decisions...She says she will run away & join the circus if she has to...Hearing those words were enuf for me to take her words seriously enuf to find out the laws in Florida...Thank-you for any help or advise...