Manipulates others to get what they want
Before You Begin
Pause and breathe. Even if this shouldn't be happening... accept that it is and embrace it with composure and calmness.
Calmness is the only way forward because without calm, there is no possibility for receptiveness and connection. Your child won't give to you any more than they see from you.
Never forget that a strong connection is fundamental, as there will be no correction in them if there is no connection with you.
The Core Problem
The core problem may be related to a lack of understanding of appropriate ways to communicate and get needs met, trying to get something they know they shouldn't have to begin with, or a desire for control.
What Will Make It Worse
Giving in to their manipulation or ignoring the behavior will both worsen the situation.
Inconsistency in setting unacceptable behavior will also not stop their manipulative tactics.
What The Child Needs
1. To believe they can achieve what they want transparently: Discuss that the best way to get what you want is to bring it to people's' attention directly. If the people around you have a clear understanding of what you want, they can work with you to get it more easily.
2. To understand why manipulation seems like the best option for them: If the child isn't comfortable asking for what they want openly, it's a sign there is probably something bad/questionable about what they're asking for. They should switch to getting specific approval first and then direct help instead.
3. Clear consequences: Clearly communicate what the consequences will be in the future every time they take the path of manipulation, so the child truly feels that option is not worth it.
How To Have The Conversation With Your Child
Find a place free of distractions where the child will feel comfortable talking freely.
Begin the conversation gently, expressing that you have noticed the child isn't openly asking for what they want at times and is instead trying to get it in secret by misleading others.
Continue with empathy, expressing that you know the frustration of not having what you want, and when it is reasonable you are there to help.
Work through the list of what they need in a tone that makes them feel like you want them to be happy just as much as they want it, and doesn't push them towards shutting down.
Ideally your child comes away from the conversation understanding that when they are in situation where they need others to achieve a goal, it makes the most sense to pursue it openly with others' support.