Why? Her belief is based on the Chant.
That verse says nothing about receiving divine revelations from the Maker in one's dreams, a claim which still ignores the whole abandonment issue without giving any theological justifications.
Perhaps she is the Maker's agent, how does one know? How can you dispute something that cannot be proven?
That's not how it works. A claim must be supported first, if it can't be supported it is meaningless and not worth engaging with. Note that I'm not talking about the context of the religion itself, not about what I as an outsider and atheist would consider meaningful evidence.
andraste herself according the codex examination of the Wrath of heaven chant, started the same way
Exactly. As I said, Leliana is essentially putting herself on the same level as Andraste, which should at the very least raise some eyebrows even among the most progressive and charitable believers.
And her actions, whether for good or ill is left for only for the Maker if he exists to judge. But what she does want, setting the Chantry on the path to virtue and charity, trying to remove persecution, how can one not see that as good and decent?
What is good or decent has no bearing on what is theological truth. Of course I'd rather live in a world shaped by softened-Leliana's beliefs ... as long as she manages to remain stable in her fuzzy-wuzziness this time around. But that is beside the point. The problem I have with "find your own path to the Maker" is that many people tend to be lazy and can easily ignore reflection and questioning (yes, I continue to harp on this a lot) in favor of simply following whatever whims they already had. Which renders the whole issue meaningless.
Perhaps it is no concern to you. But it seems to me you desire absolute certainty when life nor religion is like that.
No, I desire some indication that Leliana actually gives some thought to her beliefs, that she engages with the canonical doctrine instead of simply ignoring it when it does not suit her, that her faith is about something more than her need for unconditional love and acceptance. It seems to me that the Maker is supposed to fill a similar role for her that Marjolaine once did, then the Warden, then Justinia: the center of her emotional world and the source of her stability and self-worth, except this "person" ever so conveniently can't disagree with her or die on her. She feels strongly about something? It must be because the Maker wants it too!
This sh*t is dangerous. Uncritical faith in the divine truth of your own convictions is one of the quickest paths to tyranny, and we know how much Leliana's personality can twist back and forth, even with the caveat that some of the easiest and most extreme flip-flopping could be due to bad writing.
If she's just any random nobody picking and choosing from her religion's tenets on a whim, it doesn't matter. I'd expect many people do that to some degree or another. But when she's in a position of religious power and authority, she needs to do better than just go by her wants and feelings. Most of all, she needs to demonstrate the willingness and ability for critical, intellectual reflection, especially in the light of her own unstable history.
As Justinia says, "Idealism is the chantry's stock in trade. A religion without ideals is tyranny." It's simple, Leliana sees the Chant as a social architecture for society to lead to virtue, Shouldn't that be the only justification a religious person needs? If that doesn't satisfy, then it doesn't.
Of course it doesn't satisfy. You don't need religion for any of that. At the end of the day, religion is not about what the believers want or need, it's about seeking and serving the will of the deity in question. Obviously that's not exactly a walk in the park, especially with a deity who is said to have abandoned the world, but it is what you sign up for if you subscribe to that faith. That is why I have far more respect for the likes of Cassandra or Mother Giselle as believers than for Leliana as a believer, because they engage and examine -- or even for Varric, who at least admits that he kind of hopes it's true simply because he likes the story and the musical numbers.