At first it looked like a total nonsence to me because there's definitly nothing like that in Russian language and, even more, it's almost impossible to pronounce it. But then I realised somebody probably just forgot to switch keyboard from Russian into English and with English keyboard that would be 'FIGHTLY GIKL', so (with two spelling mistakes :)) he called you 'nightly girl' :)

It's looks like riddle :) My version: he called you "fighting girl", that is "боевая девченка". Боевая - it can means "решительная, активная". Например: "- Я добилась того, чтобы мне быстро вернули деньги. - Да ты боевая! "

I think it's the first letters of some wit saying

俄罗斯人经常用боевая这个词来形容人的性格 ））很厉害 很猛 很彪悍 很犀利的意思。。

А? O_O