I don't think you are going to find many examples of quotes that reflect Abigail not having power. The entire driving force of the drama is on Abigail being able to generate enough power to cause the witch trials out of her own will. Given the fact that the drama opens in the middle of the action, after the girls have danced in the woods at Abigail's own suggestion, Abby has already proven that she has power. She has been able to convince the other girls to follow her even though they know what she is suggesting is against the rules, indicating her power. As the drama continues, her power increases. Elizabeth speaks to this and it is brought out in the trial. Where I think that a case could be made for a moment where Abby's power is on the decline would be in Act IV, when Abigail has run away from Salem with Parris' money. It becomes clear at this point that she has left because she has been able to read the town's repudiation of the trials and proceedings, suggesting that her power is on the decline. Assessing how Parris speaks of his niece running away and the reaction of Danforth might be one area where one could see quotes or ideas relating to how Abigail's power is waning. Naturally, the ending that indicates Abigail might have run away to a whorehouse in Boston could be another indication of how Abby's power is decreasing.