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Sindel was evil because she was under Shao Kahn's control but she broke free and turned good.
Jade was never evil as far as I know. She was reluctant to help Kitana in MK3 but ended up helping her.

Sindel was never evil She has always been good but was resurrected under Kahns spell which made her evil. She eventually broke free.

Jade was supposedly evil at one time but when the time came to choose between loyalty to Kahn or her friend Kitana, she chose her friend and her cause for good. I guess she was always good.