My mom doesn’t keep kosher and asked me to cook her something treif. She gets very mad when I refuse. Is there any leniency to cook it for her? Does it matter if it’s milk and meat or not? Is there any resource online in English that explains the ins and outs of lifnei iver?
You can not cook anything that is basar b’chalav under any circumstances for your mother. As for other treif there also poskim that forbid and it is best not to. These two prohibitions have nothing to do with lifnei iver but with your own transgression. In terms of serving treif for a friend or relative who doesn’t keep kosher if it will lead to strife if you don’t then you may rely on the fact that it was available to them and as long as you are just putting it down but not hand feeding them there is no lifnei iver or mesayeia.