Complex sentence: Historical consensus is that Sackville-West misinterpreted period customs; until the mid-nineteenth century it was normal for heterosexual women to share the same bed when there was a shortage of beds or to discourage the advances of heterosexual men.
Split into simpler sentences: Historical consensus is that Sackville-West misinterpreted period customs. Until the mid-nineteenth century it was normal for heterosexual women to share the same bed when there was a shortage of beds or to discourage the advances of heterosexual men.