Just been thinking, most of us find Sumbul immature, naive, doormat and someone who has no idea what's going on. But what if it's all an act!!
First she teamed up with Shalin, because she knows he can protect her from other housemates. But when that plan backfired , she became part of the mandali and became favorite of its Leader Sajjo. Now Sajid himself has said he will ensure Sumbul gets to the finale, exactly what she wanted. She needed someone strong to save her from nominations and housemates attack. She also started picking fights with Priyanka, her biggest competitor when it comes to fans and votes (not counting Stan/Abdul, since they are in different category)
She reminds me of Rupali Ganguly (anupama) from season 1, who used to be such a doormat, and went far in the game by being so. May be Sumbul is doing the same thing, there is no way she is not understanding Sajids mockery and bullying, she is 19 not 9. She might be taking that all on to keep him on her good side. If this is her game plan, then it might have just worked.