If you've beaten konquest, you don't need to use Mileena. She's actually probably the hardest character to get a 10+ hit combo with. Just quit and come back and Shujinko will randomly transform into another character. The easiest character to get lots of hits with is probably Liu Kang. Just do one of his pop-up combos then bicycle kick. Try this: in pao choi style 4, 1, 1, u+2, bicycle kick. The bicycle kick adds 8 hits to the combo totaling to 12.