When Eobard Thawne unlocked the secrets of the Speed Force, time itself became malleable to him. He could alter timelines, editing out anything he didn't like. He first turned this ability upon himself, altering those events of his past that had angered him the most.
After becoming the head professor of analytical dynamics at the 25th century Flash Museum, Thawne (in the past, before he became the Reverse-Flash) obsessively tried to find a way to tap into the power of the Speed Force. One day, his research was interrupted by a message from a Central City Science Today reporter named Rose, who wanted to do a profile on his rapidly rising career.
For Thawne, it was love at first sight, but his heart sank when he realized Rose already had a boyfriend. Seeing this, the future Thawne (the Reverse-Flash) edited time so that Rose's boyfriend had died a week before she met Eobard. When this resulted in Rose being too depressed to be interested in a relationship with Eobard, the Reverse-Flash further edited time so that every boyfriend Rose had ever had died in tragic accidents shortly after meeting her. This made her feel like she was cursed, causing her to seek solace in Eobard's waiting arms. She was still not interested in a relationship with Eobard, however, and when she rejected him yet again, the Reverse-Flash angrily edited time so that Rose had been struck dumb at the age of five. With this disability, she never became a reporter, and Eobard never fell in love.