Mystra did come across as a bit off to me.
I think of it from Gale's perspective. Here's this ultimate fantasy, right? He's intimate with a Goddess! Not just a Goddess, mind you, but a Goddess of the one thing he loves the most: magic. It's obvious why this feels great to Gale. But then... Gale gets a little bit older and starts to look around. Wait, he thinks. I understand why I liked that, but why did *she* like that?