She's looking at someone else and they're making her happy.
Perhaps Clare and Klare are getting together.
Or, something the Priest is doing is making her happy.
It's the look of an observer - it's possible she doesn't expect the person / people she's looking at to see her / look back, necessarily.
It's also the kind of look you give to someone who's doing something touching / moving / sweet. Definitely something good, in her eyes.