Mathemagics (Chicks in Chainmail)

Mild-mannered suburban mom Riva Konneva is more than she seems. Riva, a warrior woman from an alternate reality, has come to the planet of the pen-pushers to give her daughter the kind of education that she never had back home. It meant that she had to learn a whole new way of fighting, with paper rather than with the weapons to which she was accustomed. The pen, as they say, is mightier than the sword. On the other hand, there are times - especially when old enemies arrive out of nowhere, intent on slaughtering one's children - when paper alone just won't do the job...