Breastmilk- halal or haram?

Hi mummies, I'm just curious about my breastmilk. I'm Christian and eat pork but my sister in law is Muslim. We are both breastfeeding our wonderful LOs. Is there such a thing of a non-halal breastmilk? And can her baby drink my breastmilk? I just want to be sensitive about such things esp when it comes to religion and our babies! Thank you!