I'm not sure there should be some magical age-gate on redemption. Emotions don't disappear with age, older people aren't immune to forces of pressure, and ultimately her interactions after the Exile makes her see the error of her ways seem to be fairly genuine. Add in the fact that her fall only happened after her greater impact on the galaxy stopped happening, in near-isolation on Telos. Her actions affected people, yes, but a fairly small pool of them and the 'continued pattern' only set in, again, after her isolation on Telos started, and ended with LS Exile sparing her.
It's certainly possible she's been faking her wandering this whole time, but so could have Atton in his early days, or Visas, and they weren't saved by scorn. Being wary is fair; being overbearing about it however, isn't.
Bastilla's 'excellent record' is spending most of kotor 1 arrogantly moralising, cracking and nearly helping Malak win the war and then retiring to have a kid until she was found again.
Atton fucking murdered people, tortured them, as part of an actual factual death squad - he was an adult, a soldier, a hunter of people. That's not something you can just brush away as 'screwed up young' if we're applying the same standards as Atris. And we gave him a chance.