Something that the games really failed to capitalize on was Krystal's loss of Cerinia and her coming to the Lylat System, finding a new home among the Lylatians and Star Fox. Fox denying her the chance to help defend and protect her new home was unfair. I'd wager she'd have given her life to protect and save Cerinia, so why wouldn't she want to do the same for Star Fox, the Lylat System, and Fox himself? Krystal's lost so much more on a quantitative and qualitative scale (her home world, her culture, her history, her family, everyone she ever knew etc) but Fox has also had his world destroyed what with his father dying. They're kindred spirits and Fox shoving her away led him down a bad path, just like how when Krystal pushes Fox away she become Kursed.

It would've been very interesting to see her story explored more, for sure.