(Further probing revealed that ladies and Sci-Fi are preferred.)
So, the Sci-fi part is a bit hard. Generally speaking, I watch a fair bit of Sci-Fi, but I don't read much. This applies to Japanese output as much as US output. I've seen a fair number of Sci-Fi anime, but haven't read as much manga in that genre. That said:
These first two are series that I only fairly recently discovered, and so actually have decent writeups of that I don't feel the need to revisit and see if I said anything about them that I wouldn't say now. (Not that I revisited posts on the others. Just saying.)
Karakuri Odette: A relatively short and absolutely adorable series about a teenaged girl who is actually a robot, and who goes to high school. Very very little actual science, but lots of adorableness with Odette making friends and learning about humans and human interactions and becoming obsessed with cute things.
7 Seeds: The only series I'm recommending here that isn't licensed in the
US, and probably never will be. This is a post-apocalyptic series about 5 groups of youths who were cryogenically frozen as a last ditch effort to save some of humanity from a meteor that was expected to wipe out most if not all human life. (My favorite team is the team of "rejects" who were only sent along just in case the teams made up of more prestigious members of society ended up being a bit too precious to survive post-apocalyptic Japan.) The various teams' pods were meant to only release them when environmental conditions were once again safe for humanity, but it's possible that they actually simply broke down. There's a huge variety of characters, both male and female, and a big emphasis that no one type of person or set of skills is better than the other. There are four main narrators, two male and two female, but the male narrators have less POV focus after their respective teams' backstories are told. There are parts that are thoroughly depressing and several volumes made me think I might gnaw my fingers off from fretting, and it is wonderful.
Basara: This is a post-apocalyptic manga by, Yumi Tamura, the genius who is also the creator of 7 Seeds, and it's ALSO a post-apocalyptic series with lots of female characters, but one that is COMPLETELY DIFFERENT IN EVERY WAY. (Except that with Tamura's huge casts, she ends up reusing basic character designs, which can get a tad confusing.) While
As you can probably tell, I'm not completely rational about the series, as it's one of the earlier series I fell madly for, and it's been one of my favorites for years and years. The series is licensed in the US, but some volumes are out of print. The publisher, Viz Media, has it available in digital format, though, and it can probably also be acquired through the library system.
Claymore: This one is fantasy, though there are some sci-fi elements going on off screen, and this is the only series here whose target audience isn't female. Claymore is an action series about part-demon women who go around their country slaying demons who pray on people. And then things go fubar and the organization they work for may or may not be evil and there may be rebellions and teams of swordswomen in black leather that make the entire fandom swoon. The warriors are all raised to be stoic loners with no personal connections, and so when we meet them, most have only had one or two important personal connections since childhood, if that. It's part of the shounen action genre, in which "we fight and yell at each other a couple times and then are BFF" is A Thing, and so its more reserved approach to the protagonists making personal connections is rather different from most shounen manga, and its primarily female cast is pretty unique. As a warning, it really is a very violent series, and body parts tend to go flying a lot.
Pretty Guardian Sailor Moon: A much lighter series than any of the above save for Karakuri Odette. This is about a girl who discovers that she's the reincarnation of the moon princess, and has to find the reincarnations of her guardians, who are all named after planets. This is one of the big classics of the Magical Girl genre, and rightly so. The characterization can be rather basic, but in a good way if that makes sense, and the series just assumes that it's perfectly natural for all the destined guardians of the universe to be female (eventually, there are so many that you literally lose count, and it's glorious. Rather like Claymore, but with hearts and sparkles instead of flying bodyparts). And while there's a central romance, it never really takes attention away from all the girls and their friendships, and the boy in question has a habit of getting abducted, brainwashed, and poisoned, sometimes in combination.
Skip-Beat: This one actually has no sff elements at all, and I'm including it because I would feel like I was committing a crime against my soul if I didn't. Skip-Beat is about Kyoko, a veryveryvery traditional and obedient girl who quits school and goes to Tokyo with her boyfriend to support him in his career as a rising ambition. Except it turns out that said boyfriend is actually running around with other girls while she's cooking for him and working to keep his rent paid, and brought her along to be a housekeeper. point, it gets good because then she swears she will get EPIC REVENGE by...becoming a more famous idol than he is and sets off with singleminded, vengeful ambition. Except then it turns out that, well, she's actually GOOD at acting, and enjoys the work. Kyoko can be ruthlessly singleminded and analytical and vengeful one second and then squeeing over something cute the next. She also possesses the superpower of turning every single one of her rivals into her reluctant fangirls, and pretty openly platonically (or so we're told) crushes on the first of them, Kanae, who sometimes finds herself internally warring with her pride vs Kyoko's expected enjoyment of something cute and girly. it sometimes gets sidetracked by the (fairly reasonable) angst of the male lead/Kyoko's love interest, Ren, but never for too long, and is better than many series about not forgetting about her when that happens.