But it is not obvious where the border lies between brainwashing/indoctrination and simply sharing information. If we are discussing a mutual acquaintance (let's call her Alice) and I tell you that she did some not nice action yesterday, you may have a desire to shun her the next time you two meet. Is that desire "your own"?

One could say that it is because you simply used your knowledge of her past actions to decide for yourself that you should shun her. On the other hand, one could say that I basically am controlling your actions, because me telling you what I said has affected your actions.

You can very easily yourself make lots of other borderline cases like this, and in fact they come up in real life very often. Consider the case where parents "indoctrinates" their kids with their religion. When the kid grows up to follow that religion, was it the kid's own choice? Again, we find that the distinction is not complete. If the kid had not been raised to that religion, he likely would not be following it. But this is how most people in the world got their religion. I doubt that you go around to everyone and say that deep down they don't really believe in it... But that is a separate discussion.

Anyway, what I am trying to say, is that for every desire one has originated, their likely was some (external) reason why they have that desire. Like me telling them how nasty Alice had been, or their parents telling them that god exists. (And maybe Alice was nasty, or maybe she wasn't maybe god doesn't exist or maybe he does, but that has no relevance.) In any case, that desire was caused by the outside factor, which shows that it is not very meaningful to try to separate out which desires where caused by outside factors. (As they all are to some extent or another.)