Quote Originally Posted by grafrich View Post
'За' seems to mean 'to go past, or beyond' here then. I knew about 'она залетела', but hadn't thought of it as 'crossing a border.' In English we can say 'he/she crossed the line' meaning that they transgressed, broke some moral code, fell below expected standards of behaviour. Is that sort of how 'залетела' works in this sense?
Not exactly, but near it.
First of all in russian we have 'он перешёл черту' in the same meaning as english "cross the line" idiom. "Пере-" as "over-" in "overpass".
But prefix "за-" produces another idiom in similar sense: "он зашёл слишком далеко" which is "went too far" in english.
And "Зашёл" and "залетел" do really have similar mental image derived from prefix "за-" meaning "crossing some border". This "border" can have different nature: "он зашёл в реку по пояс", "птица залетела в окно", "мяч залетел за забор", "он зашёл в гости" and so on. But there is point of interest (time/place/behaviour and so on) which was "overpassed" and perfect form of verb implies it.
There is no moral evaluation in "она залетела", just idea of overpassing and maybe flying as some quick or high/important act.
There is noun "залёт" with much broader meaning "very bad situation / circumstances", for example "вот это залёт!".