@Steve *******
extensions of stays issued inside the country by immigration offices are sold as NO re-entry :O That's because you're already IN thailand when you apply for an extension.
Once she would get the yearly extension (that would match your year entry stamp you get when you stamp into the country on the O-A visa) she would BUY a re-entry permit (either a single re-entry permit for 1000baht OR a multiple re-entry permit for 3800baht.