At 21 a person is not very mature regardless of their life, 21 is still a bit passed childhood. If her boyfriend is very young it might be because she is at his mental age. If she is not bored with him then they are of the same mindset. What does she expect from him? What are her expections in life? A home, a job, a degree, a career I doubt they are taking about grownup stuff. More like what is your favorite group, nightclub, party place, etc