Yeah, unfortunately I’m dealing with the stripe of protestant that thinks Rome is the Whore of Babylon. I tried to bring up Catholic stuff before and pretty much got told “No we’re right and you’re wrong, Catholic really don’t believe in the Bible and worship saints and don’t believe in grace.” I’m quite sure if the conversation would need to take place, it would have to be done without any explanation or justification - simply because my justification would only serve as a point of attack.
I’d do it on the phone with a friend right there, make the announcement, and then finish up the call as soon she starts making noise.
I definitely wouldn’t argue with her. During the visit, I’d say, “Mom, do you really think you’re going to convince me with arguments or I’m going to convince you? Let’s just enjoy our visit. You can come to church with me if you’re interested and you can judge for yourself.” (Then take her to the best parish and the best priest in town.) Weekends are busy for priests, so it may be hard to snag one for lunch or dinner on the weekend, but maybe Friday night? Then you can say, “Why don’t you ask Fr. Jim? We’re having dinner/brownies and coffee with him on Sunday night.” Priests are busy on the weekend, but this does seem like a very good cause. Fr. Jim would need a warning, of course, as to the nature of the visit.
I would carefully choose one or two books and at some point in the visit (once you’ve run out of other resources), you can pull out the book(s) and say something like, “I’d really like you to read this and once you’ve started reading it we can discuss it as you go along.” Nothing polemical, of course, just something VERY substantial like a Catechism or maybe the Navarre Bible Gospels and Acts or their Letters of St. Paul if you are feeling very brave. Then the next time your mom gets argumentative, you can say, have you started reading yet? If the answer is yes, you can ask her about her impressions and block out some time to listen. If the answer is no, you can tell her that the conversation will have to wait until she’s started reading. Then repeat in future. If she reads more, you’ll listen. If she doesn’t read, you say you’ll wait until she’s read more. And see if you can have a friend handy during your scheduled conversations with mom (and yes, they should be scheduled).
I don’t guarantee any results, but it seems like a good time to start.