Considering that Catherine unceremoniously bails on Heathcliff by marrying Edgar Linton, Heathcliff goes pretty easy on her. Heathcliff does disappear for three years, but when he finally accuses her of betrayal, he frames it as disloyalty to herself. Brontë offers all sorts of smaller examples of treachery – such as when Isabella runs off with Heathcliff and Edgar disowns her, or when young Cathy violates Edgar's prohibition against leaving the grounds of Thrushcross Grange. The novel presents more examples of people doing what they want than examples of people abiding by the dictates of loyalty. Betrayal, like revenge, drives much of the plot. If Mr. Earnshaw had not brought Heathcliff to Wuthering Heights in the first place – violating the family's boundaries and possibly even betraying his wife – the whole mess would never have started.
Even though she goes against the yearnings of her own soul by marrying Edgar, Catherine does not see the marriage as a betrayal of her love for Heathcliff.