The line this question refers to is the last line in Canto I of this poem where the process of Belinda preparing herself to face society is described in great detail. In particular, Pope uses various sylphs and fairies as agents of this process of Belinda readying herself, as the context of this line makes clear:
The busy Sylphs surround their darling care;
These set the head, and those divide the hair,
Some fold the sleeve, whilst others plait the gown;
And Betty's prais'd for labours not her own.
Betty is a familiar name for Belinda, and thus the last line refers to the way that Belinda is praised by society for her beauty and her appearance. Note how this final line makes it clear that the process of making herself beautiful is not one that Betty is responsible for herself: she gains praise from society for something that isn't the result of her own work. Pope here is making a satirical comment on a society that judges by appearances alone and where praise is given to people for work they haven't done. In reality, sylphs aside, Belinda's beauty has very little to do with her own efforts and is the result of carefully trained servants who work very hard and receive no praise for their efforts.