Mary Ellen Pfeifer, a Florida native, grew up in Orlando and began vacationing on Sanibel in 1969. She earned her Bachelor's in Biology from UCF in 1985, followed by a Master's in Biochemistry in 1987, during which she conducted research for the USDA. At UCF, she became the first female coxswain for the Men's Varsity Crew Team, participating in prestigious regattas like the "Head of the Charles" in Boston. Before leaving UCF, she donated a large shell collection to the Biology Department, which is still displayed today.

After completing her education, Mary Ellen worked for Bio-Rad Laboratories, selling analysis equipment to hospitals and research labs, breaking sales records and becoming the top agent in the country. She married Eric Pfeifer in 1990, and the couple moved to Baltimore in 1993, where Eric joined the family business, Maryland Screen Printers. Mary Ellen organized the company’s first nationwide catalog and led their NASCAR racing sponsorship program.

In 2001, the Pfeifers moved to Sanibel, where Mary Ellen joined the board of the Children's Education Center of the Islands (CECI), launching its first fundraising event, "Reach for the Stars," now called "The Beach Ball." Over the years, Mary Ellen has worked with several Sanibel non-profits, including the Sanibel Sea School, the Sanibel Community House, and SCCF. She played a role in creating events like "Octifest" and starred in the film "Sandbars to Sanibel" to benefit the Historical Village.

In 2011, the Pfeifer family hosted a fundraiser to help SCCF preserve the Bailey Homestead, shortly after Eric participated in "Dancing with the Island Stars." In 2013, Mary Ellen created Serving Sanibel, the charitable arm of Pfeifer Realty Group. She served on SCCF's Board of Trustees from 2014 to 2019, helping guide the organization through key developments, including the acquisition of the Sanibel Sea School and the transition to a new CEO. She also joined the Board of Trustees for The Charitable Foundation of the Islands (CFI) in 2016, where she helped develop their website and social media outreach.

Mary Ellen has collaborated on numerous film and art projects for the community. Her six-year partnership with Emmy Award-winning filmmaker David E. Carter produced five documentaries in the Pfeifer Documentary Series, covering topics such as "Growing Up on Sanibel" and "Sanibel Before the Causeway." These documentaries have raised over $30,000 for local non-profits and continue to be used for fundraising. The Pfeifer Vintage Photo Collection, started in conjunction with these films, has digitized over 3,000 historic photos, which are available at the Sanibel Public Library.

Today, Mary Ellen works full-time managing Pfeifer Realty Group's internet marketing, maintaining the website, and overseeing campaigns that enhance the visibility of their real estate listings.