In the book New Moon, by Stephanie Meyer, Bella hallucinates when she is in danger. She purposefully acts out and participates in dangerous activities, such as riding a motorcycle, because these hallucinations allow her to "see" and "hear" Edward again. Because these visions only occur in Bella's imagination, Edward is not able to see or hear her in return.
Although he is unable to see Bella, Edward is aware of many of the dangerous things Bella has done or planned to do because of his adopted sister, Alice. Alice has visions of the future, which include Bella's adventures and dangerous stunts. Even if she chose not to share these visions with Edward, Edward can still read her mind and learn about them on his own.