Is it permissible for me to marry a woman who is twelve years my senior, a Filipina who recently converted to Islam, given that there are doubts about her past before Islam?

There is no religious impediment for a man to marry a woman older than him, provided she is religious and of good character. The Prophet, peace and blessings be upon him, married Khadijah, may Allah be pleased with her, and she was older than him. However, differences in age, language, and country can affect the marital relationship. Therefore, it is advisable to marry someone close to your age and from among the believing women of your own country. This is advice, not a prohibition.