What is the ruling on attending and offering congratulations at a child's baptism ceremony in a church, and what is the ruling on eating food from a woman who openly declared that her conversion to Islam was solely for marriage, while she continues to neglect religious obligations and refuses to learn?

The general rule is that whoever declares their Islam is judged to be Muslim, and their disbelief is not decreed merely because they do not know about purity (tahara) and prayer (salat), or because they buy a dog, or go to a church, or affirm that someone else is not convinced by Islam. As for the sister who has reached the point of فسق (open transgression), she must be enjoined to do good and forbidden from evil, and the ruling on abandoning prayer and going to churches should be explained to her. If she does not respond, then boycotting her becomes obligatory if there is a benefit in doing so to deter her. Otherwise, merely remaining silent about her transgression is not permissible. Therefore, it is obligatory to denounce her and show disapproval of her actions. There is no harm in eating her food or accepting her gift, as long as it is not from ill-gotten gains.