Sonic was out one night with Amy to show her his werehog form, but unbeknownst to him the transformative energy from the Chaos Emeralds which lets him become the werehog every night had residual effects, which turned Amy into a werehog too.  While Sonic thinks Amy looks beautiful as one, Amy ran off crying because she thought she looked like a monster.  And that's when you found her.  Nobody knows who you are, as none of them have met you before, but you know them well enough to help.