Many years ago, when I first started doing a lot of client presentations, I got some colleagues who I thought were really good at doing such stuff to help me improve (I should have hired a professional coach, but I didn't). The results were dramatic. Being a really good communicator takes a huge amount of work and practice. It isn't enough to have a good product...and it isn't enough to just be yourself. Just as professional musicians and singers have to practice to perfect their performance, so do oral communicators (particular when you are communicating with people from a wide array of cultures).
Sarah is a natural...but that's not enough. She needs to take that natural talent and polish it until she broadens her appeal to include those who are currently put off by her. For example, her folksy style is adored by most rural Americans, but urbanites I speak with are occasionally repelled. Softening that style just a little bit would still leave her rural base satisfied but would help her attract more urban conservatives and independents.
IMO, the best way to do that is to hire a professional.