@Simkin
I wouldn't worry too much about it. It is a minor plot point at best. I dont think it really is ever mentioned again outside of a comment or 2. Also, it isnt like she is mad at him or anything. If you remember she even asked/expected him to kill her after she lost/ surrendered because she thought a worrier who lost was not needed in this world.
Half of it is likely pride based as well. And she likely comes from a place where losing/surrendering heavily damages your pride (a "there is shame in losing" kind of place). But she married the one who beat her, thus her pride actually went up significantly. Meaning no hard feelings. And her brother was defeated by the strongest, to them, I bet it is thought of as an honour.