Him turning up to mass (something thats obviously somewhat important to her and part of her life, and thus shes trying to involve him in her life more) dressed like a slob, and acting up enough to the point the Priest notices and refuses him communion, sounds like he was trying to show her up or embarrass her to her community/social circle (maybe they'll gossip about her and make her uncomfortable in what was once a safe and enjoyable space, or she won't ask him to church and expect him to be an active part of her life as well anymore logic)
It's a form of emotional abuse and often used by abusive men or women to shame someone for almost 'daring' to bring them somewhere or do something with them; think about how women will get dressed up for a date somewhere but the man will turn up unshowered, ungroomed, in a sports top and shorts even when its a nice establishment. It's a form of control (whether a conscious plot or unconsciously just not caring about her) and again, an attempt to embarrass and belittle her.