Technically, the Crystal Gems are traitors to their people. It would be Jasper's job and sworn duty to bring in such people to answer for their crimes…

The worst she really did was give Steven that black eye, but I'm sure he'd forgive her for it…

Okay, let's stop for a second. She did a lot wrong, it's just justified. Yes, it's her job to an extent, but she actively tried to kill the Gems out of spite by forcibly fusing herself to an unwilling participant. After imprisoning said participant for little to no reason. I'm not saying redemption for her, or even Peridot, is impossible. But come on guys, don't be ignorant. Almost all the Gems we've seen have done something shitty. Jasper's no different.