This argument is wrong. The actions we do affect reality but there is no evidence that proves that they create a new reality. The many-worlds interpretation of quantum mechanics states that every possible outcome of a QUANTUM phenomenon is happening but in separate universes.
The assumption that our decisions ALTER reality is a bias of cognition - we like to think our free will is strong. However, it is more accurate (if less comforting) to acknowledge that our actions are a product of our reality.
Just as a reality greatly impacts an individual's action, the individual has complete agency to commit any actions; of which will have certain consequences and radiating influences, thereby creating new realities that stem from decisions.