No. there is no evidence to backup this claim.
Like it says on Wikipedia:
The Countess frequently appeared in men's clothing and even in military uniform. Some sources alleged that August the Strong made his own daughter his favorite; however, this cannot be proved.
It was a rumor going around at the time.
She was apparently of exceptional beauty and had very scandalous reputation. Just like her biological father August. But most people surrounding both were of quite similar reputation. She was presented in the nude to a future lover – Frederick the Great, no less – in public and not many thought ill of that procedure.
The rumor was apparently started (at least in its written form on which we have the best access to these rumors) by Wilhelmine of Prussia, Frederick's sister, as to be read here:
— Johannes Scherr: "Geschichte der deutschen Frauen: in drei Büchern nach den Quellen", 1860, p408 (archive.org; missing crucial pages: gBooks has them) —— citing as source Wilhelmine's memoirs, in French, vol 1, p84; p103 in the linked PDF)
It might be noteworthy that this rumor was used primarily by August's son August III, to distance himself from his hated father.
What seems clear is that indeed August II took quite the liking to Anna Karolina and favoured her much, also over his son, and that 'closer relationship' began apparently too shortly after the death of August III's mother Christine Eberhardine. So his son was simply quite jealous and tolerated further rumors.
For evaluating the alleged source of this rumor:
Almost everything that is known about this episode [Frederick's entanglement wih Anna Karolina, LLC] stems from the memoirs of Frederick’s older sister Wilhelmine. These are not to be despised as a source, for she was very close to Frederick and the sympathetic recipient of his confidences. On the other hand, she was writing long after the event and her memoirs are full of mistakes. All that can be said with certainty is that Frederick William I felt very uncomfortable in Dresden. On his return, he wrote to Seckendorf that he had been appalled by the ungodly behavior of the court there, adding piously, “But God is my witness that I took no pleasure from it and that I am as pure as when I left home and shall remain so with God’s help until the end of my days." The historian’s task is made more difficult by the reluctance of any of the participants to spell out exactly what they meant by “dissipation” or who exactly was “a kind person.”
— Tim Blanning: "Frederick the Great. King of Prussia", Random House: New York, 2016.
For context, some of Wilhelmina's quotes about Orzelska in English in — Thomas Carlyle: "History of Friedrich 2. of Prussia, Called Frederick the Great", Leipzig, 1858. (archive.org). And a general desription about August's many mistresses: — Reinhard Delau: "August der Starke und seine Mätressen", DDV Edition, 2017.
Looked at from the other side of the fence: scandals surrounding August II are so numerous, the one alleged to by his enemies wouldn't be that far off either. In terms of any morals prevailing I doubt that anything August II really did – like his treatment of women in general and Anna Constantia von Brockdorff in particular – could harm him in any way. And this incest thing was just a rumour to be compared with all his other real misdeeds …