If it seems that they are out to destroy you, just remember that in order for them to become individuals, they feel they need to break their dependence on you. They are biting through the invisible umbilical cord. If you expand your own personal life, it will give them a little breathing room.
When I would put my son under the microscope and tried to sort him out, he would say mean things like, "Get a boyfriend!" or "Take a downer"! Brat! He wanted me to back off. When I finally did give him the space, he was actually just fine. He needed the room to grow.
I think single moms are very close to their children which is good to a point. When that point arrives, its good to know how to keep a safe distance. Power struggles do not work. They will win everytime.