Simson began her career in the corporate marketing field and gained experience with IBM, KPMG, Apple Computer Australia, and Ansett Australia. In 2001, she founded RedBalloon, an online experience gift retailer based in Australia. She began the company out of her house with a $25,000 personal investment and grew it to 46 employees by 2011. Simson was CEO of the company until 2011 when she took a step back from the operational side of the business. RedBalloon also launched the stand-alone small business reward platform Redii in 2016. In 2017, Simson formed Big Red Group, a company that became the parent company for RedBalloon. It also operates the companies Marketics (Albert AI), Redii, and Adrenaline. The group was formed with Dave Anderson who purchased a 50% stake in RedBalloon in 2017.