I don't know if I have anything to add to the conversation here, but I've stayed at numerous capsle hotels around the country. I've never once had a bad experience. They might be a little difficult if you don't speak Japanese, but that's part of the adventure, I suppose.
To answer the original OP, I personally don't know of any capsle hotels in Hiroshima that allow for women, but I know of one in Nagoya. It's called "Capsle Wellby Sakae" near Sakae Station. It's 4,100 yen per night, and it's a 5 minute walk from Sakae Station exit number 8. They take most major credit cards. I can post a map if you like.