Answer:
She was very reluctant to believe that he was cheating on her.
She was reluctant to go to the party, but she ended up having a lot of fun, and even met a cute boy.
The U.S. was reluctant to get involved in World War II, until the Japanese bombed Pearl Harbor.
Most addicts are reluctant to get help until they reach the point where they must either quit or die.
My siblings are reluctant to stand up to our father, but I just can't take it, so I end up being the black sheep of the family.
He was reluctant to go on the trip with his friends.