What difficulty were you playing on?
If it was on No Mercy, there is a modifier named "Deader Than Dead" that kills your variants for real, making them unable to be revived in battle. That includes Plot Twisted and Last Hope self-reviving. (I know that because it works the same way when using a Biting Cold against P. Twisted).
You said you fought against Double — Immoral Fiber. At No Mercy circumstances, your Squigly surely would be killed by Double's SA at the end of the battle, and the game could have showed her reviving and not darker just due to a glitch (the game might not have read all interactions occurred at the end of the battle well and displayed inappropriate things, like reviving and normal colors).
Even with that, the game still can read clearly the results of the battle. If you were playing No Mercy, your Squigly really died in fact.