I think her not getting the background quest must be a bug.I agree with you, i like the slaver background more. You get for free the slave that otherwise cost 6k, and unlike her market non-slaver background version, she comes with both workaholic and perfectionist traits guaranteed. Immediately assign her the head maid title and you get +4 influence/day for free. You can then assign her a job. Assigned mine as an herald so i earn 15 influecne / day right off the bat.
You also get a very small quest that gets you 52 WEGA canisters and 12 units of gold by asking her background, which you don't get once more with her market variant.
As my number 2 choice i would go for doctor. High intelligence (i truly believe that intelligence is the definitive best skill / attribute) and high medicine (which is hard to farm otherwise)
I understand not getting the traits. As she lacks training if you just buy her. But the background quest should be there regardless.