whats the opposite to the word prevented?
That would depend on the context. For instance, one opposite of "prevented" might be "allowed":
1. Her father prevented her from going out with her boyfriend. ] = stopped
2. Her father allowed her to go out with her boyfriend. ] = didn't stop
But in another context, you might say "helped":
3. She prevented me from reading. ] = hindered my reading
4. She helped me to read. ] = helped my reading