Jo wasn't allowed to go out on hunts. That was something that Ellen had been extremely clear on. Jo was pissed about it. She wanted to go out and help gank Supernatural creatures. Her mother had never budged, though, not that you had ever blamed her. Hunting was a dangerous profession; she was just trying to keep Jo safe.
However, Jo had tolerated enough of her mother's little rule.
She had told her mother that she was leaving for Vegas. Ash had even created a fake paper trail for her mother to find. There was no way that Ellen would find out unless someone told the older woman. As long as Ellen never found out about any of this, she would be fine.
Maybe it wasn't smart of her to try and help you with your hunt. She had shown up at your motel anyway. It hadn't been hard to find it. The two of you told each other everything, or in Jo's case, almost everything. She hadn't told you that she was coming. She knew that you couldn't lie to Ellen. Her mother scared the shit out of you.
She knocked on your door, knowing that you were currently inside. She had spotted your car in the motel parking lot. Her plan was damn devious. She knew that you couldn't say no to her. It was a problem, and she loved to exploit it.
She saw your eyes turn to the size of saucers as you opened the door. Your jaw hung slack, not even able to form a coherent response due to the shock that you were in. Words couldn't describe this feeling of horror/shock. There was no way in hell that Ellen was okay with this, and you knew that.
"Baby, don't look at me like that." Her voice was smooth as velvet as she spoke. She knew just how to make you melt. "I'm old enough to make my own decisions. C'mon. I just want to help you out..."