There is great debate about the nature of Beatrice in "Rappaccini's Daughter." Some people argue that she is an evil temptress who lures Giovanni...

When Giovanni, from his window, first sees Beatrice in the garden, she is "arrayed with as much richness of taste as the most splendid of the flowers, beautiful as the day, and with a bloom so deep and vivid that one shade more would have been too much."  Beatrice dresses herself in the most flattering way possible, in a way that would emphasize her natural beauty so that she would attract Giovanni's attention and interest.  Being physically alluring could be considered the first step of luring him to his doom.

When Giovanni sees Beatrice appear to kill an insect with her breath, she crosses herself, just as she did when the flower's moisture seemed to kill the lizard.  Thus, she appears to be pious and would give Giovanni reason to believe in her innocence.  If he lets his guard down while he's around her, it will be that much easier to affect him without his knowledge, and believing in her piety would likely aid this process.  The "deep flush to her cheek" when Giovanni first meets her face-to-face in the garden is further evidence of her innocence and lack of concealment, and these could be designed to further disarm him.

As they interact, she "appeared to derive a pure delight from her communion with [Giovanni], not unlike what the maiden of a lonely island might have felt, conversing with a voyager from the civilized world."  In other words, it is possible that Beatrice is playing a sort of damsel-in-distress type, making Giovanni feel that he is special and can save her from a life of loneliness.  People like to feel needed, and if this gives him an opportunity to feel chivalrous, it would likely be very gratifying and lure him further.

Moreover, by crying out in "agony," when Giovanni is about to touch one of the large purple flowers that grows on Beatrice's sister-shrub, she likely convinces him of his importance to her.  The appearance of such genuine emotion would probably be convincing to a man who wants to believe that the woman he has feelings for returns those feelings.

In calling to him from the garden whenever he failed to come at their normal time, Beatrice would continue to make Giovanni feel special and needed, and each new meeting would result in his further transformation into a creature like her.