I take sip of beer here and there, no you are not a bad mom. Just drink right after you breast feed and limit your self to one drink. If you are not sure then just pump and dump plus give baby a bottle in between. And no drink and drive of course. Otherwise relax and enjoy :)
Once the alcohol is out of your system its also out of your milk so no need to pump and dump and waste precious milk :) If you have enough milk to express the next feed and if she will drink from a bottle just do that to ease your mind :)
You're not a bad mother. I don't know if you've seen, but I have seen at Babies R Us the alcohol test strips that test for alcohol in the breatmilk. If you are concerned about having alcohol in your milk, you might consider testing before feeding her.