She is still legally a child and yes this is a shock but before fighting this take a moment to think about the best interests of the child and whether your anger and upset is about your own hurt feelings.
16/17yo is a very difficult time. You feel like an adult in many ways, the strain of being under parental control is huge but you do need some support. A lot of kids whose families can afford it will go to boarding school for 6th form having been at day school up to age 16 as the distance and space can be helpful.
Do you love and trust your sibling to look after DD well?
Are there major disagreements on important matters of belief and culture where you are on one side and your sibling is on the other and DD sees this as a way of "choosing sides"? If so then the important thing is to emphasize that families can still love and care for one another even in the face of huge differences of opinion, and make sure DD knows that you still love her.
In fact the number one priority whatever has triggered this is making sure your DD knows that yo love her absolutely and unconditionally.
Using legal means to force her home against her will is not going to solve whatever problems have led to this revolution. However, that doesn't mean it's good to just accept it - that could be taken (in an adolescent brain) as meaning you don't care.
In the cases of sharing residence of children between divorced parents, the courts may order a particular pattern of sharing when the kids are young, but once the kids are old enough to know their own mind the courts will not force them to comply and spend time with a parent they don't want to. I think the same would apply here.
This is also a far preferable outcome than DD running away from home and trying to live independently in a big city, vulnerable to massive exploitation and tragedy.
You may need mediation to help you and DD talk about what has gone wrong. After such talking, see if DD might agree to come back to you for at least a few days during each half-term break and at least a couple of weeks each full-term holiday at summer, Christmas and Easter, during which the two of you can rebuild bridges.