I hated them. They were obnoxious, lacked creativity, and smelled weird. I was a very willful child and loud about it, so I obviously refused to use these gifts in any capacity, but I think my refusal to play with toys I didn't like holds true for most children. If your cousin's girl didn't like the Barbie, she probably wouldn't play with it.
The whole point of childhood is having an idea of "I" without having a strong idea of identity so that we have a solid reference point for learning about the world without experiencing the blind spots that ego identities often impose. Consequently, we demand what we want and refuse what we don't want without thought. We rarely make compromises and our needs and wants cannot really be reasoned away by others (because our needs and wants in childhood are more instinctual/subconscious/impulsive than they are logical and experience-based).
I think we are most free to choose in childhood. By adulthood we have developed functioning identities and feel obligated to stay consistent with our idea of self. Many people take portions of their identification from a society's expectation of them, which is when freedom of choice becomes heavily blurred.