Dr. Sombilla served as a Post Doctoral Fellow in the International Food Policy Research Institute (IFPRI) based in Washington DC (1990-1995) immediately after graduation from her Doctoral Program. She worked with the Environment and Production Technology Division and was greatly involved in the development of the initial version of the IFPRI model IMPACT. IMPACT is a trade model that provides long-term projection of supply, demand, and prices for major agricultural commodities. The output of her work was the major input for IFPRI's 2020 Vision Project that aims to develop a shared vision and a consensus for action on how to meet future world food needs while reducing poverty and protecting the environment. She later joined the International Rice Research Institute (IRRI) as a Policy Economist (1995-2004) where she managed a number of research projects in Asia focused primarily on helping rice farmers improve their production, income and welfare. While at IRRI, she was assigned Officer-in-Charge of the Liaison, Coordinating and Planning Unit that provided her the experience of marketing the Center's programs and projects to development partners. Dr. Sombilla has served as consultant to several international and local organizations, including the Asian Development Bank, International Fund for Agriculture Development, Agricultural Center for International Agricultural Research, Department of Agrarian Reform, and Department of Agriculture.

Before she assumed the position of RDD Manager in July 2009, she served as SEARCA's Consulting Services Department Manager from 2005 to 2009 where she was responsible for the overall management of development projects and other initiatives especially those related to promoting agriculture growth and natural resource management. She had been actively involved in several locally and internationally funded research projects and had served either as Senior Project Economist or Study Leader.

After completing undergraduate work, she joined the National Economic Development Agency as an Economic Researcher where she developed a number of project proposals and documents concerning the agricultural sector. She also served as Graduate Assistant at the University of Minnesota wherein she earned her Doctorate Degree in Agricultural and Applied Economics in 1991. She acquired her Bachelor of Science in Mathematics and Master of Arts in Economics from the University of the Philippines Diliman in 1975 and 1980, respectively. She is member of the honor societies Phi Kappa Phi and Pi Gamma Mu, and has written numerous articles and papers on the subject of agricultural economics. Currently, she is the President of the Philippine Agricultural Economics and Development Association and a member of American Agricultural Economics Association and International Agricultural Economics Association.