Liz wanted to throw something at him.  If she had found a rock at that point she would have too.  She was able to breathe as he took a step away.  His ego infuriated her to the point that she honestly did want to hurt him.  She moved away from the sharp rocks in her back and then threw a punch.  She had no idea if it would hit or even where.  She did know that after feeling him against her, that it probably wouldn't hurt.