Was because he was the dream prince she was dreaming about e.g when Pip asked her honey do you really think your dream biy exists. She says Oh Pip I know his out there somewhere, so when she falls into the magic wishing well and becomes human she falls for the attorney Robert.Edward on the other hand didn't look a thing like the staute she made. So although techinqually Robert was the one to wake Giselle up doesn't mean that everyone should hate it just because she didn't choose Edward. After all he ended up marrying Nancy who wanted someone to sweep her off her feet.

P.s ITS JUST A MOVIE AND GET OVER IT