You mentioned family meetings as an approach to dealing with a strong-willed child, but indicated that it works for children 4 and older. What about a strong-willed 3-yr-old who absolutely has to have everything her own way and goes completely ballistic if we don't do exactly what she expects?
There are many factors that could be involved in your situation. You could be contributing to "power struggles" through your discipline methods. (I don't know, because you didn't tell me what you do.) Often, children who rebel have parents who use controlling methods. Your child's temperament is another factor. Another is your child's stage of emotional and psychological development—the stage of initiative vs. guilt, according to Erik Erickson. There are other factors, but let's put these three together and see how they might influence behavior and discipline.
Your child is obviously going after a strong sense of initiative in a big way. She needs lots of guidance with an absence of punishment. Since she has a strong-willed temperament, power struggles will only increase through punishment. Time-out might be helpful; however, it should never be used to punish, but to nurture and empower. Don't we all need "time out" once in awhile to cool off and calm down until we can behave more rationally? Children DO better when they FEEL better. Time out should be positive to help children feel better. Don't try to make your child sit on a chair, unless it is a comfortable chair with a teddy bear for him to cuddle. You might even take time out together to sit in the chair and cuddle. No, this is not reinforcing the misbehavior. It breaks the cycle of discouragement that creates the misbehavior and helps the child be ready to DO better. (When you take time out with her, it can help you feel nurtured and empowered to do better also.)
After you are both calm, you might work together (as soon as she is verbal) on solutions to the problem. A powerful positive discipline tool is to decide what you will do, not what you will make your child do. For example, when she has a tantrum, kindly and firmly leave the room. (Please read the article, "I Need a Hug". Another example: if bedtime is a problem, when she doesn't stay in bed (after a bedtime routine that has included stories and snuggling), kindly and firmly take her back to bed without saying anything punitive. You might repeat "It is bedtime" briefly, kindly, and firmly every time you take her back to bed. Remember the focus is on what you will do (take her back to bed) instead of trying to make her stay in bed.
You will notice I keep using the words kind and firm.Kindness shows respect for the child and yourself. Firmness shows respect for the needs of the situation. Avoid all lectures. She isn't hearing them anyway.Use very few words when words are needed: "Time to pick up toys." "Time to get dressed." When she argues, simply repeat the phrase. I hope you are giving her lots of limited choices: "Do you want to wear your blue pajamas or the yellow ones?" Children are more cooperative when they can have some power that is constructive. It is also effective to get her involved in helping you—cook dinner, clean, set the timer for how much time it might take to pick up toys.
I'll bet your daughter is very bright. Many advanced children are more difficult to work with. Ineffective discipline methods only increase the problems.Positive discipline methods not only are effective, they help your child learn important life skills. You may enjoy the books Positive Discipline for Preschoolers and Positive Discipline A-Z, both of which are filled with hundreds of nonpunitive methods that help children learn important life skills.