In a family brought up in the traditions of the Service, self-immolation in the call of duty is what you are supposed to do. Karen is at it as well (in my head canon she is using Edwin and his poor motherless children as a safe excuse to run away from Oxford), not to mention poor Peter at Dartmouth, though at 13 he doesn't have much choice.

I do wonder how Rowan rationalises the bit where Giles, or their father, is going to come back and run the lot at some point. Does she see it only as a short-term stop-gap sacrifice? Though at the time, she doesn't see it as a sacrifice, she sees it as a practical solution all round and thinks she can cope with it because she is used to coping.