To fill in a bit of backstory, my husband's and my car broke down in late November so since then we've been without a car. Most days I have been riding in to work with my next door neighbor, who works for the same company as I do, though in a different department.
Today marks the second time she has slept in and made me late for work. The first time I was able to wake her up by banging on her door but today I was not able to despite repeated knocks on her door and had to take the bus to work, thus arriving about forty minutes later than normal. My boss has been very accommodating about my lack of car thus far (and my hours are flexible as well) but I don't want to put her in the position of wondering when I'm going show up for work.
The reason that my neighbor sometimes sleeps in is that she's online until the wee hours of the night, sometimes as late as 2 or 3 AM and we have to be up by 7:30 to get to work "on time" for 8-8:15 (to take the bus I have to be out of the house by 7:20, in fact).
What is the most polite way to let my neighbor/coworker know that I want to take the bus from now on? (The reason being that she's proved herself somewhat unreliable.)