Yes, suicide is not specifically indicated in the text, but the score (or at least orchestrations) were altered to fit the moments of her swallowing the beans.
As I see the song, the Witch has given up and holds such contempt for mankind that she recklessly strews the beans, potentially destroying the world ("giants by the score"). Honestly, I see it in the same vein a mass shooter or a terrorist...or Sweeney Todd or one of the assassins in ASSASSINS. The frustration and impotence festers until it explodes. It's then directed outward on the world. Suicide then seems in keeping with this mindset and makes perfect sense to me in this context.
Is it written specifically in the text? No. Does it feel a little "tacked on" as an afterthought? Sure. Still, though, it was a directorial choice that was an interesting idea and clarified the moment. Couple that with her turning old and ugly before our eyes, and at least we now get what happened to her rather than left wondering why she just descended into ground.