Know-it-all MIL, help!

My boyfriend's mother is a nice person, whom I believe means well...but...she's such a know-it-all control freak! I don't even know if she realizes what she's doing when she's constantly butting into other people's lives and stuffing her opinions and advice down their throats (and mine). It's so annoying, and honestly, quite offensive when she's constantly saying I'm wrong or doing things wrong because they're not precisely how she would normally do them. Basically, if it's not her way, it's the highway, and she gets super offended and bitchy if someone goes against her...even if it's an opinion. She's so downright belligerent and rude sometimes that it's caused arguments, simply because she refused to listen to others and interrupts, increasing her volume and amount of words as to rule the conversation til the other party gives up in frustration. I'm at my wit's end with her, but I do love her because when she's not driving me insane, she's a great lady. I don't want to screw up our relationship, but I feel like I have a Monster In-Law. Help!