Lady Anne knows Richard III murdered her husband and her father-in-law. She curses him, his hypothetical children, and his hypothetical wife. Richard somehow talks her into marrying him, though. He says, “I’ll have her, but I will not  keep her long.” And she says,

“For never yet one hour in his bed
Have I enjoy’d the golden dew of sleep,
But have been waked by his timorous dreams.
Besides, he hates me for my father Warwick;
And will, no doubt, shortly be rid of me.”

So what happens is she curses herself. And then Richard III kills her so he can marry a younger woman.