Female leads in chinese manhwa are pretty vengeful usually (at least the ones on mangadex).
She says she's in love with her Master...yet she's saves the Demon, flirts/hangs out with him, and uses him. I get it...the Demon Lord treats her well, so she's willing to let him off the hook for mass murder. But if you're keeping "option 2" open in case "option 1" doesn't work out, you're not that committed to Option 1.