Anna Karenina's basic karmic theme is that love nor happiness can ever occur if it involves sacrificing the feelings of others. In other words, only self-sacrifice (not sacrificing your family, current lover or husband, children, or others around you) is the causative factor of happiness.
Under this umbrella you find several other themes in Anna Karenina which are directly linked to that statement: Infidelity, abandonment, treason, jealousy, hypocrisy (societal), and the ardent furor of lust which is often confused with love.
Anna's curse was that she left those who loved her to follow a man she went crazy in love for. She found in him the ardent furor described before, as well as he did. He was a dandy and heart breaker who needed his next prey. She was the easiest of preys. In the end, both realize that what bound them together was temporary, yet, they had single handedly changed and ruined the lives of those whom had to endure their decisions. Hence, she ended her life.