Fiona:

   although you mention more than once tha mom is healthy... and I believe
you.. some how there is a weakened area in that breast that is not able to
"withstand" any insult...Or this infection had never really cleared up..
cleared enough for mom to be asymptomatic for a time and then she is ill
again.

    is it possible to do some homeopathic things to aid her immune system?

    are they testing before treating to find the most effective antibiotic and
then using it for long enough?

     Susan Love discusses removing the gland or tract in which this occurs.
she considers it rather minor surgery and does it under a local. .. if you can
locate a copy of her book it is worth reading this passage... if you can not
locate let me know...

       Patricia