Ok. Here's a few things I see going on here. I hate to say it, but once they go nose down, tail up, they are usually dying. However, for furture reference, here are some issues:
- While bottled water is generally safer, it is still advised to always use dechlorinator, as it removes more than just chlorine. Also, if the water was distilled, it would kill the fish.
- A blood worms-only diet is not nutritionally balanced and can lead to constipation. It is possible your female is suffering from a fatal bout of constipation, common in bettas. A betta's diet should be a mix of primarily pellets, as well as a variety of frozen or live foods, and an occasional bit of frozen pea to help prevent constipation.
- She could also have a secondary infection from the injury, but I doubt it. Or, the other female could have hassled her, causing internal injury. If she does not pass on, you really must get a separate tank from her. They will otherwise eventually kill one another.
Good luck, I hope she makes it. If you could move her to a shallow separate tank kept at close to 80 with salt, stress coat, and maybe even some collodial silver or blackwater extract, it may help, however, the stress might be too much at this point. Sorry =(