Fancied he might be sweet on the missus, that's all, explained the girl, adding with an appearance of sulkiness: "How you do take one up!"
The girl explained the reason for what she did. 
mnli hypothesis: The girl explained the reason for what she did.  premise: Fancied he might be sweet on the missus, that's all, explained the girl, adding with an appearance of sulkiness: "How you do take one up!"