I can be quite an opinionated person, so I've tried to think of the things that might work with me!
Have some things that you reserve for just you, DH, children etc. Not to be unkind, but because this would remind me that you are a separate, capable, family unit, where you and DH like to make the decisions.
Don't be afraid to say some of the phrases posters above have suggested. "That's not my way", "I prefer..." etc. It doesn't have to be confrontational, but stops her taking your silence as agreement.
If there are things you don't want her to be involved in, don't mention them to her until they are complete. Talk about things outside of the family, work, news, neighbours, friends etc that you won't feel judged when she comments on.
Good luck. She sounds like she cares a lot, just is a little much for you at times. It sounds fixable!