Rarity the trading card. Also kinda weak like Pinkie Pie 'cause, well, she makes dresses for a living. Her pump ability makes her an interesting add though, having the "other ponies get..." makes her not overpowered and can't be a bringer of doom.
Okay. It took a second for the "black" part to fit in, but she can be a bit self-centered at times, until her better side kicks in. Again, "Other pony creatures", possibly adding "you control" to the end.
I can't tell because of the watermark: is the second option +0/+1? (Probably, as the zero would be preceded by a minus otherwise.) If yes, pumping toughness with black mana would be... off. Seeing that Rarity already is WB, you could make the activation cost colorless without raising any questions. The flavor text suggests that her ability is related to whining, but I don't see the connection if she pumps instead of crippling (which would have issues of its own).
I used her dress-making talents for the reasoning behind her activated ability. I made it expensive because clothing only really does so much, but in a pony deck she can make everything really big or really tough or a little of both, and at worst she's still a 2/2 for 2.