It doesn't translate to maid either. https://translate.google.nl/#nl/en/werkster If people say they have a "werkster" the woman is usually is a female, doing cleaning work. But in a factory she could be doing anything. A maid https://translate.google.nl/#en/nl/Maid is more a young female worker, also doing things like taking care of the children, shopping, washing etc.. Where a werkster is not necessarely young. I think "employee" is an acceptable translation for "werkster".
I've seen a lot of theories behind the custom of considering the names of months and days to be proper nouns, none of which is especially satisfying. For days of the week, the prevailing theory appears to be that the names of the deities for whom they were named kept their proper noun status when, for example, "Thor's day" became "Thursday." Similarly (but not as tidily), inasmuch as March was named for Mars, it retained its status as a proper noun, like the god. It is a less compelling explanation for months, given that September, October, November, December are numbered months (that no longer correspond to their positions in the calendar, but that's another story). However, once a custom is in place, it becomes, well, customary.
According to www.VanDale.nl...werkster has several meanings:
werkster 1 (woman, female) worker 2 (schoonmaakster) cleaning lady - See more at: http://vandale.nl/opzoeken?pattern=werkster&lang=ne#sthash.HZTI6eCr.dpuf
So, should "werknemer" be used instead for "employee" and is "werkster" more accepted as maid?