They used "dear" here, I checked the raw it's 旦那様 in the raw. I think a more accurate choice would be Master here. Especially with how she's calling the son (it's bouchama at one point). Actually maybe it's better to just use the japanese Danna-sama here, since who knows maybe it could be important for future plot.
Edit: Okay I'm reading further now, and yeah I think it's better to use the Japanese here instead of forcefully trying to use English, because the way it's set up feel like it's meant to be a "change in meaning" thing due to plot. It's Ars-bouchama at one point, but then it's Ars after that.