mastitis after breastfeeding

I mostly nurse for bonding only once a day. I'll pump right after since my baby drinks an ounce then passes out at my breast. I noticed the breast I nurse her at gets minor mastitis even after pumping. At least I think it's mastitis. It's been a more recent thing. Anyone know why? I know they say your body doesn't know the difference between a pump and a baby but sometimes I feel like that's bullshit. Maybe she doesn't latch the right way or doesn't pull out the milk properly.