I’m gonna headcannon: So the dress wasn’t just turned black (I mean it may have still looked cute even if it was black, because black wedding dresses are awesome anyway) But what the black fairy did was actually burn the dress, making it all dry and brittle and it eventually disintegrated into nothing but ashes. Now as to why Regina couldn’t just poof one up into reality? She did, the one Emma is wearing was poofed up by Regina. Or better yet poofed up by Emma. Who decided “aye I want my wedding to be original so I’m not going to wear my moms dress, I’m going to wear some other ladies dress”.
"I could have the giant duck as my steed!" --Daniel Radcliffe
Keeper Of Tamara's Taser , Jafar's Staff, Kitsis’s Glasses , Ariel’s Tail, Dopey's Hat , Peter Pan’s Shadow, Outfit, & Pied Cloak,Red Queen's Castle, White Rabbit's Power To World Hop, Zelena's BroomStick, & ALL MAGIC