I dunno of it's that different in japan but 220k yens is around 2k USD which isn't that much... Maybe Japan's economy makes it a good salary....
Edit: the average yearly salary is around 37k USD in japan which makes around 3k USD monthly.... So she's bellow average... She is confident that she'll get a promotion though if you can consider that she's a young woman with a good career ahead of her then 2k for now could easily be increased over a few years.
Japan's houses are around 4k/sqm, we're talking about a fully reinforced concrete house here of course.