Books that have a girl made a lady in waiting/scullery servant to a horrible mistress and using her own skills/cunning fights her way out of her low position in life

[Regina]

And maybe even find romance or at least a better position like a princess in a Cinderella esque fashion or find better life situations and maybe adventure

I liked the Claidi journals by tanith Lee and Ella enchanted, just Ella, ever after, a little princess

[Shanna_redwind]

Poison Study comes to mind. I'll look through my books for others.

[Heather]

This is a book I read in middle school years ago, set in ancient Egypt, and is still a fave now, Mara, Daughter of the Nile.

[Ann aka Iftcan]

I can second both of the suggestions made so far.

[Christine]

I'm not sure if Vanity Fair has already been recommended? The classic, by William Makepeace Thackeray.

[Rainbowheart]

A Little Princess is maybe too obvious?

[Regina]

Yeah that last one I've heard of

[☯ DαякєηRнαℓ ❛ ᶜʳᵒᵘᶜʰᶤᶰᵍ ʰᵘᵐᵃᶰ ; ʰᶤᵈᵈᵉᶰ ᵗᶤᵗᵃᶰ ❜]

Not sure, but this came to mind, a great read:

[Lobstergirl, au gratin]

Pamela somewhat fits.

[Karen]

Here are books were the heroine is in a low situation and uses her smarts to work her way up. Some of them are not the traditional maid and maiden dynamic though:

The Midwife's Apprentice: The oppressor in this case is not a single mistress but the whole village. The heroine is not a maid but more like a homeless lass. She turns her life around with her own wits and skills.

Lyddie: She's a factory worker so her oppressor is the factory manager and life in general. But she fights to make a better life for her brother and herself.

Homeless Bird: This is my favorite (close tie to Midwife's Apprentice). The oppressor in this one is the mother in law. This book is about a young Indian wife. She reaches the bottom of the bottom of Indian society and makes a new life for herself with her wit and skills.

Book of a Thousand Days: This is the one with the most traditional maiden and maid dynamic. However, the maiden in this case is more spoiled than cruel and she's not the main character's (the maid's) number one oppressor. It's actually an evil king who wants to marry the maiden. The maid turns around her life with her wit and skills.

[Laurel]

A Little Princess by Frances Hodgson Burnett fits. Girl at an expensive boarding school loses her money when her father dies, and she is made a servant in the school

[Mandy]

The one that come to mind that I have read recently is:
A Spy in the House