In both sentences she thinks it's sexy and she is surprised that it is. But I have to agree with Bill, there's a slight chance she hasn't decided yet. This is how I see it: The first means more like she didn't expect herself to find it sexy. The second she was sure that it wouldn't be sexy but it turned out to be.

No quite, in the first she now thinks it is sexy, in the second she it is not clear if she has decided that it is sexy