Combine 'slice of life' with superpowers, heroic fights, add a dip of magic, and give it a little girl x girl x boy twist (though very, very minor). Fairly regular stuff, although not too bad. What made it stand out and interesting is the 'sisters' arc, especially in the spin-off, which is a lot darker than the rest.
A Certain Magical Index
This is the original series, which led to two spin-offs and a movie. On Netflix I've found the original series, as well as the first spin-off series. I'm not sure the second spin-off was ever released in the west, Netflix certainly doesn't carry it.
A young non, a stranger to the world, is implanted with the knowledge of a hundred thousand forbidden books, and enters the life of a boy called Toma Kamijo. The world he lives in is a world with magical and non-magical superpowers. He himself does not have a 'real' power, but he seems to be able to break or block others'.
Now throw in twenty thousand clones, only created for a little experiment, and suddenly things are no longer light hearted.
A Certain Scientific Railgun
The first part of the second series is fairly dark. If the whole series is typical Japanese anime, then I would still suggest (for those who can stand a little gore and anime in general) to have a peek at season 2 episodes 1 to 16.
On Netflix you'll also find the movie, which I found a little disappointing.
Yes. Worth watching. My suggested order to watch:
1. First watch Railgun, season 2, episodes 1 to 16.
2. Then watch Index, all episodes.
3. Then watch Railgun all episodes.
Yes. Effectively you'll be watching Railgun season 2 episodes 1 to 16 twice, but I think it is worth it.
Now, the only question left is: does she get the boy, or does she get the girl?