Hello, is it acceptable to purchase a meal for someone sitting shiva during the 9 days? (it is not exactly a “gift”). And, when buying kosher food for Jewish people, does one have to be responsible for their level of kashrut? (e.g., making sure they did not eat meat before serving dairy to them?)
Yes you may purchase food for someone else to eat during the nine days. You should be careful to give them kosher food, but you don’t have to worry that they might be flieshig when you give them milchig, (unless they are ignorant and don’t know the halachos).