Yeah. And "to let her live as a human" is an awful reason to abandon her to live as a stray dragon in human lands. Counterproductive too!
How can you say it's counterproductive when Dorami is living a perfectly happy and fulfilling life right now?
Also makes no sense why the mother remained living as a human there instead of returning to her beloved husband as a dragon, if the reason she lived as a human there was to let dorami live as a human.
Because it's the only place where she can live as a "human", due to the place being so cold that nobody thinks twice about a person never removing their hood. Maybe it's not an awfully social place either, at least not that small village. But she still wants to live as a human, even if it's a lonely life, after, apparently, getting tired of running from blood-thirsty adventurers for her whole life as a dragon. Tired enough to accept a divorce.
But like you said, the worst part is how she unilaterally decides that her kid is happier without her in their life, for no real reason other than maybe "I already abandoned her once, so I am likely to do it again if I reconciliate, and break her heart".
This I naturally agree on. She seems to believe that Dorami will live happier as a human, with no imperfectly transforming other dragon around her. Anyone could tell her that's pure bollocks, as long as the kingdom officially accepts her as well, granting her the protection. She would probably face very little persecution, especially if folks knew she's the most famous adventurer's friend.