This is called a "reclining nude" - made famous by Renaissance Master Titian. Nearly every famous painter after him has had their own rendition of a reclining nude, it's almost a right of passage.
That being said, this is not a strictly erotic painting. Note the faint Harem pants covering her legs, and the cloth covering her face and lower arms. More than likely this would be a painting of the lady of the house. Although she is sexualized, it is more to display the power of her husband - he has the money and strength to not only have a babe, but also hire a painter to paint her beautiful figure.
Also note the craqueleur of the painting - literally the cracks on the surface of the oil paint (almost always happens to oil paintings). Although craqueleur can happen nearly immediately (as oil never technically 'dries') for it to be this extent would require a good deal of age of the painting. This furthers my belief that the painting has remained in the possession of the manor for a rather long time, helping me understand its a member of the household.
Lastly paintings were brought to lords of various noble women to marry (like tinder in the Middle Ages), and they would pick the best babe - this could be her betrothal painting. This isn't very likely however, because these paintings would be very non-erotic, dressed in full court regalia usually. Just another possible thought.
