I would relax a bit....Finding four "bugs" in a couple of weeks in your house is definitely not an infestation. Most mites are so small you can barely see them. Having one budgie in your house is not a cause of any infestation. If you post a good photo of one of your bugs when you find the next one, and an estimate of it's length, I should be able to identify what you're creepy residents are, or at least give you a good idea of the family. (I do live bug educational programs).
If you left a large amount of seed in open containers, all over the house, for a period of time, you could have a variety of insects that may feed on it, but I'm curious of what your cousin identified her bugs as?