I mean she did threw away her responsibilities as the highest ranking leader position of a vast intergalactic empire because she was bored and felt pitty for a bunch of hairless monkeys, she did cause a vain civil war that lead to the deaths of numerous gems, both rebels and loyalists to the point where only three members of her rebellion are left. She did kept the fact that she actually a Diamond from the rest of the Crystal Gems aside from her Pearl, which broke the trust of the Crystal Gems, she abandoned Pink Peral and Spinel like they were just toys that got boring and annoying. Didn't see that her whole rebellion could mean the extinction of her species since gems need to colonize and terraform planets to reproduce.
I'll tackle these in order, but a lot of what you've said here is simply not true, and the stuff that is true isn't that bad when compared to alternate options. This is gonna be a long one because there's a lot to unpack here, so bare with me.
Firstly, no, Pink did not hold the highest ranking leader position, that spot solely lies in the hands of White Diamond. We know not all Diamonds hold the same level of leadership because of Yellow and Blue bending the knee to her, and also because the other diamonds repeatedly (before Earth) neglected Pink and did not trust her with anything important, let alone a colony.
Second, no, it was not because Pink was bored or pitied the humans. Up until this point the planets that the diamonds had conquered did not have intelligent life (direct quote from the crew), and after being exposed to such Pink did not think it was right that the planet be wiped out regardless. Her visits to earth and the vast amount of life on it changed her perspective, she began to value all life, it was not pity.
Third, yes her intervention with the Earth colony led to a Gem & Human war but this conflict was almost certainly inevitable. Her options were to masquerade as Rose and take a stand against The Diamonds, or try and reason with them as Pink Diamond. But we know her talking to them wouldn't work based on how prior conversations of her trying to talk to them had gone (her prior plea created the human Zoo because The Diamonds interpreted her concern as her wanting Humans as toys), they'd simply ignore her concerns, take her colony, and wipe Earth completely. War isn't great, but you have to weigh a war against the extinction of an entire planet. Billions of humans, all the different ecosystems and life Earth is a home to.
Fourth, yes she kept her identity as Pink Diamond a secret from most of the characters, but that is hardly a bad thing. The shakeup was only temporary as well as near the end of the show, and Pink is hardly the only character to use a white lie to protect others, let alone the only character to lie in the series. The lie simply maintained the facade of Rose Quartz so that the Diamonds would leave Earth alone. While this was only temporary after the flash, given Yellow wanted The Cluster activated, things would not have died down nearly as much if The Diamonds knew Pink was still alive on Earth. They would wage an unending war to retrieve her.
Fifth, Pink only left Spinel behind. Pink pearl was taken from her by the other diamonds and she was replaced by the pearl we're familiar with. Spinel is her own can of worms, you could ask why The Diamonds never went to Pink's Garden when they were maintaining her things (the last Rose Quartz gems, the human zoo, ect), but as far as the narrative is concerned Pink leaving Spinel behind was a flaw in her character, RS stating that Pink had a tendency to act without thinking about how it would affect others. This is definitely a mark against her character, but the part about her abandoning Pink Pearl is not true.
Lastly, no, the gems survival was not hinging on the colonization of Earth. We're never shown, nor is it alluded to anywhere, that the gems are close to becoming extinct. They have countless colonies already established throughout space, alongside Homeworld STILL popping out new gems. Pink standing against The Diamonds to protect earth was not putting her own species at risk of going extinct.
Ufufufufu. Yes ;3
Is a strange fascination I have. A weird cosmic world that is ment to test your sanity and courage.
I mostly like it on games. Dunno why but anything remotely similar to Lovecraft stories is a go for me.
Not same thing as Eldritch because it may be weird as Lovecraft but his stories are focused also in mystery not just the spooks.
Pink Diamond Portrait (Personal) 
Cotton candy :D 
Yidhra 
( OC ) At the beach <check description for another picture> 
Obscuria 
The Binge Eater 
R33L Piconjo vs Faek Piconjo