Liver flushes don't interfere with breastfeeding, in fact, they help make the milk more balanced and healthy. A cleaner liver removes blood contaminants more effectively, which helps the breasts produce better milk. The stones and toxins the liver releases are released bia the bile ducts and intestinal tract, joining other waste that the intestines release. For any toxins to enter the breasts of a breastfeeding mother they must have accumulated in the their connective tissues for a long time, or the blood must be very toxic to begin with. Many pregnant women do liver flushes also during pregancy and found it to be very good for them and their babies.
If you do liver flushes, make sure to cleanse the colon before and afterwards.