It seems HP knew that Jackie had two pistols, why does he let her keep the second one? Ch 31

Warning, SPOILER ahead.

Being carried on a stretcher was a “cringing” and “frightened” Simon Doyle who lost his “boyish insouciance.” He frantically apologizes to Jacqueline for revealing their plans. Jackie reassures Simon by telling him it was ok — “a fool’s game, and we’ve lost. That’s all.” She pulls a second pistol out from her sock and proceeds to shoot Simon and herself. Mrs. Allerton asks Poirot if he knew of the second pistol to which he admits that he did. Poirot realized that Jackie managed to slip the second pistol into Rosalie’s bag during the day of the search. Jackie later retrieved the gun from Rosalie’s cabin. Mrs. Allerton asks Poirot if he wanted Jackie to go out the way she did, to which he responds, yes. He understood how she felt and what she would do. He allowed her to go out the way she wanted and stated that “Simon Doyle has died an easier death than he deserved.”