She was only 19 years old (with a degree in Communications from Maryknoll College- now Mirriam College) when she took over their shoe business started by her great grandfather, Don Laureano Guevarra, "Father of the Philippine shoe industry." This served as her training ground to her present investments such as the First Quadrant and First Vita Plus.
First Quadrant is a Multi-Level Marketing company, which has received negative speculations and was tagged as a pyramiding financial scam. However, it has stood up and is now recognized as a legitimate multi-level marketing company. It basically sells items like Avon does. It has catalogs with the products made by Filipinos (among which are five brands including the Marikina-made DOYEE shoes and D. Tactacan Shoe Manufacturing), wherein the seller gets commissions from the sales. Moreover, First Quadrant supplies and manufactures shoes for Oleg Cassini, Lady Rustan's, SM Elegance, Milani, Styletto, Chateu Bourghesi and Rebecca Taylor (New York).
First Vita Plus is a natural, organic power-herbed, dalandan-flavored juice drink which has received numerous testimonies that it cures ailments from insomnia to kidney stones. 
Doyee, the sister-in-law of senator Mike Defensor, is indeed a successful entrepreneur who uses the motto "Filipino First," in her businesses.
- Caragay, Nene. Filipino First, Doyee Tactacan-Tumpalan. Quezon City: ABS-CBN Publishing, c2006. (read on November 28, 2007).
- "Entrepreneur Business Exchange." (accessed on November 28, 2007).
- "Mike Defensor’s First Quadrant in pyramiding scheme — DTI." (accessed on November 28, 2007).