can you tell me why so many people including ex-Catholics, are convinced Mary is worshipped
Josiah is not going to be happy with the off-topic talk, but one last tangent to answer your question: I can speculate in general, but it may vary from case to case of course. But your question is little different than the scads of ex-Christians altogether who are convinced Christians are delusional or that Jesus didn't exist. The numbers are ultimately irrelevant to the truth.
If the Catholic Church were the true fullness of Christ's Church, then it would stand to reason that persecution would be aimed in the Church's direction. So that's one possible answer.
As well, in 21st Century America there is little to no capacity to recognize the difference between the worship due to God alone and the awe given to a saint like the crowds in Acts 5 did for Peter. People will equate asking for someone in heaven to "worship." It's a fallacious notion on its face. This may also be due to those outside Catholicism trying to convert those within Catholicism that don't even realize asking a saint for intercession is the same as asking a saint on earth for intercession, like Paul did so many times when he asked others to pray for him.
Also, those observing from the outside, or even poorly catechised Catholics from the inside, often do not have the grasp of the theology that a well-versed Catholic does. As a result, they erroneously equate kneeling in front of a statue as "worship" when that is also nonsensical on its face. Not only are there abundant examples of people kneeling or bowing before someone else in Scripture that isn't due to worship, but the person on the outside has no business making claims about what the kneeling person is doing in prayer.
Finally, you might want to pick at your friends' brains to get to the real heart of the matter. Too often, there is some peripheral problem they have with the Church which results in their eagerness to believe various myths advanced by the ignorant. For instance, a lot of former Catholics are not comfortable with the notion of contraception. No free sex whenever I want? Well, that Church stinks! I bet they worship Mary too! What, you won't grant me my annulment? Agh!! You are an evil Church! I should confess to God through a priest!! I'm not comfortable with that!! Masturbating is sinful?!!! I reject your teachings! You worship Mary too! Maybe they even are scandalized by abusive infiltrative priests and extend the anger to other teachings without merit. Like I said, case to case varies.
There are often deep personal wounds behind the rejection rather than an honest rejection of the theology. We can know this because when asked to support their claims on Catholic theology, they are unable to cite a single authoritative thing from the actual teaching office of the Church. It will be how they felt, or what they perceived about kneeling, or they thought the mass was "boring" or whatever else.
Now, I hope I am not one to scoff at another's personal wounds. But even so, true teaching is true teaching, and myths are myths. You probably incur the same myths from skeptics. "Christians think an invisible man lives in the sky." "Christians think prayer is magic." "Christians think the Bible fell out of the sky from God." "Believing in Jesus is the same as believing in the 'Flying Spaghetti Monster.'" Heard that one? Do a web search some time. There are plenty of misconceptions to go around, not just about the Catholic Church (although I would agree with you there are a lot of people who think about the Church as you say---we just disagree about their degree of expertise on actual Church teaching or the theological perspective of those who actually practice the faith.)
Finally finally, even if this nun was a real person, I would still say the best place to go to understand a Church's theology is someone who is authoritative on that Church's theology. Not some ex-member who might have a personal bent. For Catholics that would be the Catechism. For the Lutherans, perhaps the Book of Concord or Luther's large or small catechisms. For "Reformed tradition" it's the Westminster Confession. I would be awfully cautious and ready to cross-check claims of some disgruntled ex-Reformed guy who could have just walked out after an argument with his pastor and decided to rip on everything else about what that congregation "supposedly teaches." In other words, if there were a dozen priests in the U.S. who left the Church and tried to tell everyone about how Catholics worship Mary, and then there were the remaining 47,988 priests who think Catholics don't worship Mary, then what nonsense is it to prop up the "ex-priests" as "experts" who are the ones who got it right? Especially when they can't cite you a single authoritative doc to support their claims.
Sometimes it's like a bad breakup. Some personal hurt feelings occur in one of the members of the relationship and then they can never say another good thing about their old partner again. They are even willing to spread false rumors to get back at the hurt they felt they got when they were mad about how they felt about the Church's teaching on divorce or whatever.
