As you know, I am Catholic.
That site, and similar programs within the church, are aimed at people who have already, on their own, felt a "tug" that inclines them to re-examine their decision to leave. I have known many such people. In fact, I was one of them when I came back in the 1970's (and there were no websites like this because their was no web!)
Prior to making that decision, I had had lots of people, (Evangelicals and Baptists, not Catholics) knock on my door, hand me tracts, invite me to their churches, etc. None of that swayed me, of course.
It was only when I started to examine the way i was living my life, and realizing I needed to change some things, that I began to consider returning to the Church. I did, and in my case, it "stuck." But the initiative came from within me, not from someone else.
On the one hand, there are those who are pretty insensitive in the way they try to convert people. (I've been on the receiving end of that.) On the other hand, I have also found that the mere mention or suggestion of Christianity is sometimes viewed as more "aggressive" than it is intended to be.
There is a story about Francis of Assisi. He had the idea that one way to end the Crusades would be to convert the Muslim leader to Christianity. So he actually "went behind enemy lines" and sought an audience with Sultan Malik Al-Kamil . They engaged in conversation, and of course the results were nil. But Al-Kamil said something I find rather remarkable in an age of stark religious division (to put it mildly!) He pointed out that since Christians and Muslims were at war, he really ought to have Francis put to death. But, he was moved by the fact that Francis risked his own life for what he (Francis) regarded as the fate of the Sultan's soul. And so he gave Francis safe passage back home.
(This was popularized in a movie, "The Sultan and the Saint", and that may cause many to doubt the historicity of the story. But it is not just a movie plot. Prior to the movie, there were books by historians, not Christian apologists, which told this story.)
I do not know your cousin, of course. But based on the little you have said, I would suggest texting her back saying, "Thanks. I know you mean well. But that website is not for me." She might drop it, figuring she did her duty and will not press the matter further. And then you will not be depriving yourself of the opportunity to have a renewed relationship with your cousin.
Or, she might turn out to be someone who is indeed overly aggressive and insensitive about this, in which case you have lost nothing.
