Answers (1)
Are you asking why this happened?
There is not enough information here to make a logical guess as to why she left home to go and live with another family.
People are only going to be able to speculate. More information on your family dynamics would be needed to do anything more then that and even with information a reasonable guess can be made but one can not know a persons true reasons some sometimes.
I imagine that is hurtful and upsetting to some degree though and I am sorry to hear your going through this.
People often do things for selfish reasons though it tends to be in our nature to be selfish so there must be something there that has drawn her to it. Something she is not getting or wants more then at home.
Good Luck