Need Help-Hip dislocation

Hi all,
I need some info. My sister is in on her way to the hospital as I write this because her hip spontaneously dislocated on her at work yesterday. Background, my sister is a former gymnast, very flexible, always has been. she's been complaining of leg pain (hypsersensitive skin along her leg) for a few weeks and feeling unstable in her hip.
My question, if her pelvis is unstable (it is anteriorly rotated and higher on the right than left...her left hip is the prob), can it be causing the instability in her hip? I don't know if the hip fully dislocated or just shifted unexpectedly. Any ideas? There is something from my studies that I learned about this but I'll be darned if I can remember. Any ideas?
Thanks,
Gray