I think the point is that the daughter disobeyed and she received the exact consequences that was told to her. That's part of parenting. Kids push boundaries all the time to see if you'll follow through on what you threaten. Will she disobey in the future? Sure...all kids do. She's not perfect. That doesn't mean you don't follow through on consequences. It's not an unreasonable expectation to say "X didn't change so Y is going to happen." If that's considered an unreasonable expectation, would you then tell an adult who committed a crime that they need not fear jail because obviously the threat of it didn't stop the behavior? Of course not. All children, and even adults, at times in their lives learn the hard way. This was obviously a case of that.
Of course, I understand what she did - I'm a Spec Ed teacher, and I deal with unmotivated kids all day. For me there are 2 issues - sure she is still getting a birthday party with family, but I don't think that taking away her friend party is that big of a deal to her. Only time will tell...if it was that big of a deal, she would have changed her behaviour. It's really not that simple when dealing with pre-teens and teens. We don't know what kind of parenting is happening in the home either. What type of discipline is practised in the home on a regular basis? Why didn't the daughter curb her behaviour when 'threatened' to lose her party? Is it because there is inconsistent discipline, or, because she is struggling with internal motivation? Consequences must be consistent, swift and reasonable, but they only work if you have a child who is easily motivated. If you have a child who struggles with motivation, I can assure you that pretty much nothing will motivate them to stop their behaviour. Not saying this is the case with this child - perhaps she's just testing the waters, which most kids do, as it's a normal and important part of child development.
What would she be learning if the party wasn't cancelled after she didn't change her behavior? OP warned her dd about consequences and either dd didn't belive that her mom would actually cancel the party or she didn't care. I tend to think she didn't think that her mom would follow through and she quickly learned that her mom would follow through. Now the dd knows that her actions/attitude have consequences and hopefully that will be helpful in curbing it. I know that once on vacation my dd was acting up and I threatened going back to the hotel if she didn't knock it off. She continued so we left and spent the next few hours sitting in a hotel room. To this day, my dd knows I do not make empty threats and that her actions have consequences.
What did the parents learn about their child's behaviour - she didn't stop, regardless of being threatened with removal of a party, so only time will tell if indeed this consequence worked or not. I think it's too big of a consequence for sassy talk - what kind of consequence will happen if she does something major? When you start at the top, it's really hard to gain trust, and set your kids up for success. Your hotel example is minor compared to a birthday party, IMHO. Removal of a child who is misbehaving is necessary in certain cases, but this is different. Of course, having a friend party is a privilege, but it's a pretty major consequence for that activity, IMHO. I honestly believe that if the friend party meant that much to the daughter, and she truly believed that her parents meant business, she would have curbed her behaviour. Like I said, we don't know anything about past experiences, or what kind of discipline is used in the home. There are so many variables that go into this type of situation. It worries me though that the OP in her followup was actually thinking of taking her out of the musical - yikes! There are so many kids who hate school, so why take away a school event? I have parents who take away sports and such for their teens who drink and drive, steal, etc., but for being sassy, that is very harsh, IMHO.
I think it's great that the OP didn't cancel her birthday altogether. I'd be interested to hear how her daughter has been behaving since the removal of her party?
It's hard to find people's currency - in this case, it sounds like the OP believes it was the party, but I'm really not sure about that? I don't claim to have all of the answers, but I have seen kids in which nothing motivates them (some of them didn't even respond to meds), and before everyone assumes they are all spec ed kids, not all of them are. Many kids, and adults, struggle with internal motivation, and so in my experience, the answer isn't as simple as taking stuff away or time outs.
I wish the OP, and everyone else, an abundance of patience when dealing with tweens and teens! Tiger
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). As we hadn't really made any firm plans, no invites or such had gone out, the party was "it" and honestly, I think it would have broken her heart to take her out of the musical. 
Just kidding 
