Possessive = I'd say to take ownership. Your view is that it belongs to you. Or they being to you. And they should do or act the way you approve.
Protective: one, either feel very protective about them meaning ill defend them with all I have to stop you.
But you acknowledge they are individuals and have their owns lives. Own experience and they have to learn for themselves. You can be protective, and know you have to let them go. You can try to save them and help them through, but they are independent of you. They don't exist for or because if you. Possessive they become your property and lose any identity. They become a product of your imagination
I'll add you won't have much in the way of a friendship/ relationship if you don't understand, respect and desire them to be their own people. So possessive is a bad thing. Protective, good or bad ill die protecting her.