Two consecutive relative pronouns "was": What do they each qualify?

Question

Es gibt nichts, was sie sagen könnte, was die Tatsache ändern oder auch nur rechtfertigen würde.

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For the sake of argument, we will consider:

Part A = "nichts"

Part B = "was er sagen könnte"

Part C = "was die Tatsache ändern oder auch nur rechtfertigen würde"

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At first, I was under the impression that both B and C separately and individually qualify A:

There's nothing she could say; and there's nothing that could change or justify the fact.

But I realised that it would be strange to say "there's nothing she could say", because nothing should hold her back from expressing her own opinion.

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Now, I wonder if C actually qualifies B, and B and C as a whole qualify A:

There's nothing she could say that could change or justify the fact.

= She couldn't possibly say anything that could change or justify the fact.

Here, I think the sentence means "she can say whatever she wants, sure, but she could not say a thing that could change or justify the fact".

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It might be similar to how it works in programming languages:

[ Part A { Part B ( Part C ) } ]

instead of:

{ Part A ( Part B ) } & { Part A ( Part C ) }

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I wonder if you can rephrase the entire sentence, using only one was:

Nichts, was er sagen könnte, würde die Tatsache ändern oder auch nur rechtfertigen.

Answer 1

You are correct with your second guessing:

C actually qualifies B, and B and C as a whole qualify A:

There's nothing she could say that could change or justify the fact.

And yes, if you rephrase your sentence to

Nichts, was er sagen könnte, würde die Tatsache ändern oder auch nur rechtfertigen.

, its semantics don't change.