I'm wondering, quite seriously, who's trolling whom.
Considering what you pulled with those recent posts, I'm not going to take this statement seriously. Moving on...
My own anecdotal evidence wasn't enough to show you that friendships can indeed be ended over religion. You are unable to attribute things that happen in the real world to having in game equivalents, and you are unable to accept that NPCs might be written to have viewpoints that may counter your own. All of this has been pointed out multiple times over the course of this discourse, and you're still here with "but people can't break up with you over religion". The how and why this could happen was pointed out to you. Your response: But people shouldn't break up with people over religion. Why shouldn't they?
You're making statements with no context. First off, Lavellan is Dalish, a member of an ethnic group who are known to follow the Creators, and are vilified by some for it. That doesn't necessarily mean that Lavellan necessarily has the same beliefs as the People, but it's clearly not something that should come as a surprise to Sera. Lavellan is known to be Dalish, Lavellan has vallaslin, and prior to this confrontation, it's made abundantly clear that the elven Inquisitor is one of the People. When Lavellan says that she believes in the elven gods (in this particular scenario), it shouldn't come as any surprise to Sera. Instead of accepting that Lavellan doesn't share Sera's Andrastian views, she ends the relationship because Lavellan won't abandon her religious beliefs for her.
My issue is with what Sera does when Lavellan simply admits that she believes in the elven gods, and it shows a rather ugly side to Sera. You don't date someone, have sex with them, and then give them an ultimatum to abandon their religion simply because it differs from your own; that's repugnant.
If you're too elfy, you won't get into the relationship with Sera. All the disapproval you'll get along the way will make sure that doesn't happen. So, when Lavellan dumps it on her after the temple, of course she's going to break up with you. There's two ways to look at it: You changed into someone you weren't, or, you were lying to her the whole time to get her in the sack, and either one of those reasons is reason enough to dump you. People don't appreciate being lied to, after all, and if it's the former, if you change enough, which confirming that you're too elfy would be, there's plenty of reason to dump you. I know, you don't even need to bother to type it: "But she shouldn't break up with you over religion", right?
Xil romanced Sera with Lavellan, and she was pro-Dalish and pro-mage, so I'm going to go out on a limp here and point out that it's possible to romance her while not capitulating to her every whim.
Furthermore, Sera shouldn't have gotten into a relationship with Lavellan in the first place if religion was such a contentious issue. Getting romantically involved in a relationship with someone who is from a different culture than you, and then tossing them aside because they won't simply give up their religion for you, isn't some admirable personality trait that should be defended at any cost.