The most relevant reason why this information should influence how much you are persuaded by her video is:
The payment may encourage her to give the game a more positive review than normal.
When a reviewer is compensated by a company for creating a review, there is a potential conflict of interest. The reviewer might feel pressured to provide a favorable assessment to maintain a good relationship with the company that paid her, which could compromise the objectivity of the review. Thus, knowing that she was paid can lead you to question the authenticity and impartiality of her opinions on the game.