From mine & Dom's experience it usually mean's...

she's not ignoring you, she was driving down the road, she come's to a bend in the road not realising there's black ice on the bend she put's her foot down, the back end of the car come's out, the car spin's out & hit's an oncoming bus.

Hence, she's unconcious thus not returning your call or txt's.

Rest assured she WILL return then once she regains conciousness.