Maybe Misty wanted to slap Ash at first, or even sock him, but that would be the extent to which she wanted to do any possible harm. As you said, he did technically nab something from her and carelessly have it destroyed, and she is definitely the "fiery redhead" sort.
After that though, it was definitely more of an unadmitted fascination of sorts with Ash, whether you'd call it a "crush" or not