The oxymoron 'rehearsed spontaneity' implies the pop singer's spontaneous actions are not genuine but carefully practiced, casting doubt on her sincerity or, alternatively, showing her skill in performing.
The oxymoron 'rehearsed spontaneity' in the sentence implies a contradiction since spontaneity is typically characterized by impulsive or unplanned actions, while something rehearsed is practiced and deliberate. This particular use of an oxymoron suggests that while the pop singer's actions may seem spontaneous to her fans, they are actually well-practiced and intentional. It affects the meaning of the sentence by suggesting that her apparent spontaneity is not genuine.
Both options that the oxymoron 'casts doubt upon the sincerity of the pop singer' and that it 'expresses admiration for the singer’s acting abilities' could be considered correct in different contexts. The first option highlights the incongruity between the singer's actions and genuine spontaneous behavior, while the second acknowledges the skill it takes to appear spontaneously affectionate and accessible despite the actions being rehearsed.
Without additional context, though, the primary effect is typically to suggest the former, that the sincerity of the singer's behavior might be in question due to its rehearsed nature.