I don't have Beaumont's book on "Giselle" any more -- I loaned it to a forgetful friend

-- but I think that's where I first learned about the "beckoning" gesture. It's not really contradictory.
Giselle is a Wili. She is Myrtha's servant. Myrtha's objective is to kill Albrecht. Giselle tries to save him BUT she is under Myrtha's spell.
She takes him to the cross -- as several people have pointed out on another thread. This is why the grave has to be in the forest, where the Wilis live, and why Hilarion comes, in a scene now generally cut, to make a cross to put on her grave. Because she died unshriven -- did not receive the last rites, suicide or not -- she could not be buried in the churchyard. I think all of this would have been understood in an instant by the good Catholics of Paris.
Giselle gets Albrecht to the cross, which will block Myrtha's power. Myrtha, then, has to get Albrecht away from the cross and orders Giselle to dance. Giselle's dance is supposed to be so seductive (classically speaking) that it lures Albrecht away from the cross, so that Myrtha can get him. It's all very well worked out. Sometimes the dancers aren't told these things, though, and don't tell the story; they just dance it.
The first time I saw the "beckoning" was in Alonso's performance in DC, when she was 60. Other ballerinas used a vestigial gesture, at best. The role of Giselle can be extremely complex -- she loves to dance, her "natural feminine instinct" (pagan) is to be seductive, yet her Christianity gives her charity and she wants to forgive Albrecht, because she loves him and he has shown repentance. Very few ballerinas can show that conflict. Fracci did it beautifully.
The parts where Giselle dances with Albrecht, I was told too early in my balletgoing to source it, was indeed that she "spelled" him -- gave him a break (not Albrecht the dancer, who, of course, has to work just as hard to partner her, but Albrecht the Albrecht, whose perpetuum mobile is broken by Giselle's own dancing.