Young Writers Society

•Why is Rachel officially called Rachel Winter and not Rachel Raetaregsanbanna?
Not only would the latter further support the idea that she was treated like a member of the family she was adopted in/hired for, but according to the CP, she doesn't know her true origins yet by the time the story begins. So, she shouldn't be aware that her real name is Winter, and neither should most people.
Given that the family tried to make Rachel think that her bodyguard training is a totally normal family responsibility (and that they know she's decently smart), calling her Winter would make it easier for her to, well, question and find her origins. That sounds like a grave oversight that's very very likely to backfire on them. And uh, she has a dragon. And combat training. I'd wager the last thing they want is risking to have her snap on them, which might happen if they give her a free dose of Identity Crisis.
#SephirothSaysHello

•...Why are the Raetaregsanbannas even bothering to lie about her bodyguard status?
I don't mind personally, I mean this as a genuine question. They could quite literally not do that, treat her like an equal anyway and not only would she be just as happy, she'd have nothing to complain about because A: she's still adopted, B: she gets to live in a pretty nice place, C: she belongs somewhere and according to the CP, the worst treatment she has is being expected to become a talented bodyguard, and she succeeded with flying colors.

↑ If you really wanna keep that in, I guess a possibility would be that they'd be scared of future resentment towards having to constantly protect their biological daughter, but... Actually, scratch that, because even then, lying about Rachel's origins and telling her that the intense training is because she's the eldest sister is likely to cause the exact same issue.

So, basically, there seem to be some sort of artificial conflict there, and honestly? You don't have to keep it, m'dear! Rachel not knowing about her Winter last name would already be enough, and given that she was legally adopted, it even makes sense that she wouldn't necessarily be told. Plus, there's still the mystery of her dad and you coud make 'im show up as a Boss/Important NPC encounter later, which in itself would be totally cool.

Food for thought!