Relax mama! You need to take care of yourself and if you felt you needed abx. then so be it. Yes a baby can get abx through breastmilk, but in small amounts. I would be giving her probiotics herself if she is not already taking them. My son had to have a course of abx (which in retrospect I now do not think he needed and am beating myself up for it) and it has messed with his gut and we are still trying to fix it. The fact remains that at some point in your child's life your DD will probably take abx and all you can do is try and minimize the effects. You haven't ruined her and it is not the beginning of the end! But you can take steps to minimize any abx she may have ingested through your BM.