How can I tell my mother in law to back off?

In my personal experience, I've found an email conversation/letter to be the best way to accomplish this. Start off by being compassionate and appreciative. Tell your mother in law all the things you are thankful for and all the times that you have been happy. I can understand that for some people this is hard. Not everyone is universally more positive than negative. But appreciating your mother in law is not to make her feel better (though, yes, it will), it is to get her mind open to accept your point of view. After you've shown that you can appreciate the efforts of your in-law, tell her in "I" sentences not "you" sentences what it is that you want. Don't say "You are too involved in my life" or "You are too controlling". Say "At this moment, I think I need a little more space to figure out my problems and my solutions. I appreciate your input, but I think I just need to figure this out by myself" or "I appreciate your input, however, I think this is one of those things I'm going to have to figure out by myself." Or even, "I really appreciate you being there for me and my family. We just need to spend some time alone to build the bonds you had in your family". It's tough to offer compliments to someone you feel antagonized by, but believe me, it facilitates in opening your mind to the positives in the situation as well as the person you're speaking to. Nothing is black and white. The more we appreciate the greys, the better we are at communicating and coming up with a solution.

Tell her that your marriage is between you and your partner not with her. Her influence is only harming the relationship not helping.

Just straight up tell her how you feel. Don't be afraid to express your natural emotions. She should understand, and if she doesn't just try your best to make it clear. You'll get the burden off your chest and hopefulky gain some relief.

In my experience, I will bring her to a shopping spree, listening to her blabbing all the time and not complaining about it. Then I will express my ideas of how we can get along by talking through our similar interests and how we can respect each other's presence.

Well, if she has done something wrong then I think you should not tell her anything tell someone else to tell her

If she acknowledges logical reasoning and you can convince her with your reasons, she will clear path. If that is not possible, let your significant other handle it.

Tell her you thank her for caring and watching out but that you can handle things yourself. If shes always on top of you on things nicely tell her you got it but thanks for the help and reminding.

Your husband should handle that. You shouldn't be put in that position. He needs to man up and talk to her himself

With respect - Remember she is the mother of your significant other. No matter how you feel, it is important to also remember how your partner feels. Have you spoken to them about the issue, how do they feel about it? Perhaps it is more appropriate for them to speak with the mother rather than you, or you could do it together on mutual grounds.

Respectfully, everyone has feelings and most of us always act out of the best of our intentions. So just tell her how you feel when she acts a certain way and try and show her how if she acted in a different way it would be better for your relationship.