That would be "Maid" which is a terribly, terribly outdated word (like a ~2+ centuries of being outdated, I'd guess).

No, "meid" came from the term for female roomservant (similar to maid) but it has lost any relation with that term by now and is used mostly in the derivative form "meisje", and sometimes "meid" but that is almost never said by males. Same as we have the word "wijf" which is the literal translation of "wife", but at this day and age it is a pejorative term. Sometimes words just don't literally translate to another language (or gender, in the case of "guy") without having a slightly (or largely) different meaning.

For me it's not even the age that's the factor. I refer to young women that are 18+ as "Frau" just fine. Just not those that I've known for years before that :I

I don't know how this translates between German and Dutch. It also depends on the context. When I talk to both my male and female friends and refer to a girl I think was beautiful but below 30 y/o, I am very hesistant to call them "vrouw" as it does not sound right. We just use "chick" (just the English word, no translation) mostly, also by the females. But I feel that the usage of "chick" in Dutch is a bit different from English.