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You have described in some good detail the behaviors that you are observing in Nia which are something to be concerned about.
Good behavior should be rewarded and undesirable behavior consequented. It does not seem that she had earned the reward of a lavish and expensive party.
One turns 16 only once. You can still have a celebration for her without having to spend a lot of money (it is the though that counts) Perhaps you and her mom can let her know that if she had been behaving more like a 16 yol young woman you could have tried to please her but since she has misbehaved, you feel that the party given is appropriate to her.
With all of the issues that you are describing, counseling may be appropriate if she is willing to give it a try. Sometimes family counseling (where the client and the parents attend together is helpful too because she can still be confronted yet, there will be an objective counselor there to offer feedback and help)
Unfortunately the behaviors you are describing are indicative of Conduct Disorder -