I didn't find the story or the narration engaging at all. I think that the tone was supposed to reflect the awkwardness of a first date, but it didn't work for me.
I thought that turning into an animal to reflect one's self-esteem was a good metaphor, but it didn't carry through to after the kiss. The frog got his self-esteem boost without a change in form, but Steve did get a change and didn't feel any better about herself(?) until afterward.
Steve's appearance was too sudden. Besides on or two ambiguous words earlier in the story, the revelation came out of nowhere. At first I though that it was done just so that his/her transformation could be used as an obligatory fantasy element and that if Sharon had gone home and perceived herself as more beautiful because the frog was so nice to her them the story wouldn't have lost much besides said obligatory fantasy element. Looking back, I guess that the author is implying that Steve really is the frog's princess, but I still can't get over how Steve came up at the last minute.