Gwynne is not involved in Starship. She handles the customers and related requirements, while Musk handles R&D and related requirements. For example, Musk want

Gwynne is not involved in Starship. She handles the customers and related requirements, while Musk handles R&D and related requirements. For example, Musk wanted to cancel Falcon Heavy when it started to become clearer how tiny its impact would end up being relative to cost (since F9 had improved so much as to eat up most of the demand they had expected FH to take). It was pretty fair reasoning, but Gwynne insisted that they keep FH development going because they had already started trying to sell it to customers and she felt that cancelation would affect how seriously customers take future offerings from SpaceX for rockets which haven't been fully built ahead of time.