Here is How I see it (if anyone cares)

The 2010 Alice In Wonderland is a sequel to the original disney cartoon, with a little leeway. In that film Alice learned that while it was fun to use your imagination letting it go too far was not good either. I believe that after her adventures she still used her imagination but did not go as far as she would do before her adventure down the rabbit hole. Her father did not put a damper on this either and encouraged her to have fun.

As she got older her imagination was suppressed by society as well as the presence of her mother. She still had it, as demonstrated in the vehicle as well as at the party, but instead of being welcomed it was shunned.

So when she follows the rabbit this time she is coming from a different frame of mind than the first time. While she still has her imagination she does not have as much confidence in it.

As she travels in Wonderland the second time she believes she is in a dream. As she realizes she is not she uses that imagination to help her accept the things happening around her. She eventually is able to use gain back the confidence in that imagination to believe she can defeat the Jabberwocky.

The result of this is she now realizes that her imagination is not just something that she can use to entertain herself but something that can be used in a more productive fashion as long as she does not let societies expectations hinder her.