Hi! I was interested that you think it's rude to go into a church to see a wedding to which you've not been invited - I was always told that a wedding held in a church is a public event, and that any member of the public is entitled to witness it. (Obviously, that'd be awkward if you have enough invited guests to fill the church, but still, it seems reasonable to me.)
I wonder if it has something to do with that "If anyone knows of any reason why these two should not be joined in holy matrimony..." line?
Well, for one the wedding isn't at a church, and she's not only trying to crash it (when there is only room for 50 or less) but also the reception.
2nd, many people have small weddings and have very limited space. If there were a lot of crashers, where would the legit guests sit?
3rd, a wedding is meant to be shared with friends and family. If you are not invited, the HC decided that you were either neither of those, or that your relationship
wasn't close enough that they felt you needed to be there, or your behavior is bad and they don't want it messing up their wedding.