I don't blame her, seeing as SNSD is IMHO the top girl group of Korea right now, in terms of making money and popularity.
But I still love her in T-ara. She gets a better chance to shine and get recognised for her talents, rather than be hidden in the background (as mentioned before SM likes to play favourites ;D)
SNSD actually weren't that popular when they debuted and it took them a while to reach the top. So I know that after a while our lovely T-ara, with their gorgeous looks, stunning voices and sweet personalities will become just as if not more popular than them one day. ;]