Right to not use the Breaking Point, right to bubble Bismuth and right to not tell the others about it. Even though it sucked.
It’s clear from her general demeanor and Garnet and Pearl’s reaction that Bismuth was a very popular Crystal Gem. A strong personality that was a huge part of defining the entire Crystal Gem movement. She liked the Crystal army, and it seemed to like her.
When two charismatic leaders inside of a movement have a philosophical conflict that cuts to the core of the movement itself, the usual outcome is a split in the membership. It’s almost certain that, exposed to Bismuth’s idea about shattering Homeworld Gems, some of the Crystal Gems would have agreed with her rather than wanting to stick to the relatively “non-violent” methods Rose had been using, and would want to take up her methods. This would have fractured the Cystal Gems into two weaker factions, giving Homeworld an opening to crush them both.
By not telling the rest of the Crystal Gems about why Bismuth was poofed and bubbled, Rose prevented that fracture and kept the movement whole, eventually allowing them to fight Homeworld to a standstill. Even though that really, really sucked for Bismuth.
Now, why was it a good idea to avoid the use of the Breaking Point? Apart from the obvious moral implications, the Breaking Point represented an escalation in violence on the part of the Cystal Gems could have caused Homeworld to obliterate the planet. Homeworld wound up using a nuclear option on Earth, but ultimately left it intact. While individual Diamonds may have had differing opinions on what should be done with the planet (Yellow Diamond wants it destroyed now, but clearly they didn’t all believe in that tactic at the time or it would be destroyed already), they were able to agree on simply “nuking” the world by making it uninhabitable for Gems (or so they thought) by corrupting all the Gems on it.
And saving the Earth and the organic life on it was one of Rose’s major motivations. It would seem that ultimately, the Diamonds found the Gem War too costly and withdrew, but if the Crystal Gems had managed to shatter many important Gems and posed a serious threat to the lives of Gems on Homeworld, vengeance and obliteration might have looked like a better option even if it was more costly.
So, Rose made a tactical decision that was painful, but ultimately saved the Crystal Gems. But I don’t think she intended for her decision to remain in the dark forever. I think that her choice to leave Bismuth in Lion was also tactical.
I think that the items left in Lion’s mane are parts of Rose’s life that she thought were important, or left unfinished. The presence of her video to Steven strongly suggests that she meant for him to find this place, and I think she meant for him to find Bismuth and discover what happened between her and Rose.
Rose could have hidden Bismuth some place where she would never be found, but she left that bubble there for Steven. I think she hoped that, with the war over and with Rose gone, Bismuth would be able to have a peaceful life, without being in a position where she would feel the need to shatter other Gems, or that Steven would be able to change her mind.
Either way, I think Rose felt guilty for what she felt she had to do to Bismuth to keep the Crystal Gems and the Earth safe. I hope that one day, under happier circumstances, we’ll see Bismuth again.
Edit for clarity: I don’t think Rose is perfect, and the ramifications of her choices don’t go away even if I believe it was the best choice she could have made in this situation. Even if I am right, untold Crystal Gems were shattered and corrupted in the aftermath of her choices. Clearly Homeworld and the Diamonds share that responsibility, but we don’t know how Bismuth’s theory of war would have played out, if shattering the Diamonds would have been enough to change Gem society, or what costs that tactic would have had. I’ve offered my opinion, but it’s just my opinion. Either way, I don’t think Bismuth is evil or bad. I think she saw what she felt was the best solution to a problem and believed in that the benefits would outweigh the costs.