There is a question of principle. - Principle?

这事关原则。 -原则？

Because it was a question of principle.

这是原则问题。

It was a question of principle, Ove explains to her.

这是原则问题，欧维向她解释。

But it was a question of principle.

而是因为这是原则。

Then again, she never was very good at grasping questions of principle.

不过她也不是很清楚什么叫原则问题。