1998 Dodge Durango Uncontrollable vehicle

My fiance' used my vehicle one morning and the durango kind of locked up in the back like one of the wheels were not rolling. This was explained by her to me. She told me that the vehicle was pulling her every which way. She pulled over and called me. When I drove it home it made a god awful sound in the middle of the vehicle. I have no idea what I am looking to fix. I have heard that the transfer case may have went and that the rear end may be gone. Where should I start and what can I do to find out what exact problem I have?