I recently noticed that shoujo magazines are published in all sorts of way but the weekly format is either not a thing or so rare that i couldn't find it in the printed form (but research is my job ). Both male varieties have all sorts of weekly publications so what is going on here?

Don´t misunderstand me. I dislike the weekly format (monthly is the most sensible to me) as art shouldn´t be rushed out of the door and it straight out kills authors but why is this a male phenomenon only. Josei tends to be a bit of a redheaded stepchild of the publishing world but shoujo is big. Would this form of female targeted publication be interesting to some of you?

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I also read EU/US comics and am a librarian.
Manga-Masters, My ANN-Lists + Imdb

Yes, before there was. It was know as "Margaret"
But then it went to semi monthly because the company is not getting money. Btw, shoujo sell well but not like shounen and seinen. I think it's better if shoujo is mostly monthly or semi.

Because in shoujo, they focus on the art (backgrounds, effects, flowers,...) so I don't think they can keep them up every week while shounen are simplier since they don't need flowers thingy and backgrounds are optional

The only weekly manga I've ever come across is Nisekoi Doumei! (Currently ongoing)
But even though it's weekly, its chapters take seriously 20 seconds to finish, so that's kind of annoying.

I have no idea what Everystar is but Manga Box is a (weekly) web publication so it can´t count as a magazine and the target demographics aren´t always clear too. They do publish what can only be described as half chapters but the service is coming around when compared to where it was before...

Margaret (the circulation is again slipping) went biweekly in the year of my birth so i apparently had a point that weekly Shōjo magazines aren't thing on the market and never really were. Girls deserve the same format the (big) boys get too but we frankly dodged bullet as this way of throwing together a product in the last second regardless of quality is no way to write in the long run. No wonder that so many mangaka burn out rather fast.
Monthly chapters are the best format if you ask me.

________________
I also read EU/US comics and am a librarian.
Manga-Masters, My ANN-Lists + Imdb

as of today, no shoujo magazines are currently weekly.
the closest to a weekly shoujo magazine would be online publications like comic polaris, or in if strictly in a printed manner, magazines that are printed every other week.