HA,
Yes, basically you are correct. Full rules on the government web site. ‘Travel tax’ (or ‘escape duty’ as I refer to it) is payable by Filipinos and residents. However, it is NOT payable by those on visit visas. In this case, allow me the assumption that this lady was a Filipina visiting the PI (or RP, if you prefer).
My main points still apply. The decision to bump a pax is commercial, not racial. You can take steps to minimize the chance that it will happen to you.