MIL AND SIL were BOTH like this. MIL passed away (rest her soul) and we are in the process of distancing ourselves from SIL, though we do have to deal with her due to the will, etc.
Recently I told her how I felt. I have not felt this healthy and great in years. It's so important to stand up to these controlling manipulative people! Unless you have dealt with it, you might think it's crazy, but once you go through it you realize...manipulative controlling, always right people. Gotta love it, if you want to have them in your life, create healthy boundaries. ANd then, worry about things which really matter, like your life and children! Coz they don't.