The Sisters' Punishment: Just?

I most certainly feel that the punishment Psyche's sisters received for their evil plan is just. The sisters, even though they themselves had happy lives and had no need to be jealous, destroyed her life when she was finally happy. First, they were happily married: "duae maiores sorores regibus desponsae iam beatas nuptias habent," (Chapter 2, pg. 15, lines 4-5). Not only were they married while Psyche was alone, they were happiliy married! The sisters got to be married and happy, but Psyche, who was left alone for a very long time, when she finally finds love, doesn't deserve it? No. Clearly, any jealousy they felt for Psyche was ill-founded, and it is in no way justified.
Next, what they did was deliberate. They planned it from the beginning and guided Psyche into the trap. Perhaps if they had truly been scared for Psyche's life and told her to kill the monster, they wouldn't have deserved such a fate. But they had planned it, and they were not scared for Pysche's life. It was pure jealousy. In translation, from Chapter 4, the sisters say "We'll teach her that we're not her slaves but her elder sisters. So for the present let's return to our husbands and our poor mediocre houses; and then after thoroughly digesting the situation let's return equipped to lessen her pride." There's no arguing it, the sisters intended to bring Psyche down, they flat out say it! There's no room for discretion, their intent is undeniable.
On top of this, after Psyche had been left by Cupid, they were ridiculously quick to forget about her problems and try to marry Cupid for themselves. In translation, from Chapter 9, "No sooner had Psyche finished speaking than the other, pricked-on by ravening rash lust and rankling jealousy, rushed out..and then taking ship she proceeded with all speed to the crag as of old." Psyche had barely finished speaking and she ran off! The same with the other one, "Psyche gave her the same misunderstanding; and the womanm lured by the hope of supplanting her sisterm dashed off to the crag and fell into the same death." Neither sister had the slightest drop of sympathy, let alone any emotion other than jealousy and greed. Therefore, both deserved the horrible death they got.
The sisters had no reason to be jealous, planned the evil plan with deliberate intent, and afterwards, didn't even show or feel any pity for poor Psyche. For these reasons, coupled with their undeniable evil, their punishment is just. If anything, they should have been tortured, and the only way their punishment isn't just is because it wasn't as harsh as it should have been.