I understand your feelings completely but you have to remember this only annoys you because you choose to let it. It's only a piece of paper toss it out, (tear it to shreds if it makes you fell better) scan the note for anything newsworthy and go on about your day. Send your Mom a newsy note or card and say nothing about the brochure.
As you said, your Mom is not well and one day when she is not here you will have the satisfaction of knowing you behaved decently toward her even though she (unlike Jesus) is pushing her beliefs down your throat. If you catch yourself mulling this problem over an hour or a day later, dismiss it from your head....change channels and think of something more pleasant.