I would guess that your question would refer to the Gentlewoman in Act 5, scene 1 of Macbeth. The rest of your question seems a bit perplexing, since she appears at no other time in the play.
The gentlewoman's role in this act and scene is to establish the lengths to which Lady Macbeth has descended into her guilty madness. Lady Macbeth's night-terrors and sleep-walking would have gone unwitnessed had not the gentlewoman summoned the doctor, it seems. As the scene opens, the Doctor observes that he had been watching for two nights with the gentlewoman upon the gentlewoman's report that Lady Macbeth was troubled and acting strangely. He seems a bit perturbed himself, for Lady Macbeth has failed to appear. However, moments later, Lady Macbeth appears, and she is acting strangely indeed.
What ensues is the 'Out, damned spot!' monologue in which Lady Macbeth seems to relive the night of the murder of Duncan and her grisly part in it (in which she herself collects the blood of Duncan and smears it on the drugged guards - hence bloodying her own hands).
So, you could say that the gentlewoman facilitates the scene - she puts us (and the Doctor) in a position to watch the Lady and gives us the exposition we would need to understand what is happening.
That is her obvious FUNCTION in this act. As for her description?
1) It must be noted that she would be 'gentle' herself - that is to say that she would be of high status to serve a queen. This is no mere maid.
2) Notice that the gentlewoman shows a mixture of compassion for Lady Macbeth and utter repulsion. The Doctor tells her to scurry away ("go to!") when Lady Macbeth seems to admit to such terrible things. "You have known what you should not" says the Doctor. The gentlewoman seems dismayed that the Lady Macbeth says what she did because she was there at the murder, and the woman cannot even imagine (or is afraid to imagine) what that means Lady Macbeth actually knows. The play on the word 'knows' merely emphasizes the terrible guilt of the Lady that startles both these characters.
The doctor immediately professes that he cannot cure this kind of malady (indeed, not even a priest could do so at this point - there is no real confession happening here, Lady Macbeth is senseless and asleep).
The gentlewoman's response to the monologue, however, is profound. She would not 'have' Lady Macbeth's heart (as black, corrupted, sin-stained as it is, we can imagine) for all of the dignity of her body (the Lady is the queen).
SO... Why ask the question in the first place? What does this all point to?
The gentlewoman, in this case, is not unlike the Greek Chorus. She models for us, the audience, the sort of pity and fear (Aristotle's 'cathartic' emotions proper for Tragedy) that we are compelled to have. She is a gentlewoman herself; like the Greek chorus, she is a representative of a proper class to have a position on the enormity of the crime she has been made witness to. The doctor serves as her counterpart in this, as well, and shares her concern and dismay as we should. She even mentions the very heart of the ancient tragic mode... that it is a Queen, a 'dignified body' that has fallen so low as to be loathesome.