Tricky mixed conditional

[Ricco]

Which version is correct?
1. I'm not sure whether it was Mary. I shouldn't wonder if it was her older sister.
2. I'm not sure whether it was Mary. I shouldn't wonder if it had been her older sister.

[svartnik]

Which version is correct?
1. I'm not sure whether it was Mary. I shouldn't wonder if it was her older sister.
2. I'm not sure whether it was Mary. I shouldn't wonder if it had been her older sister.

both.
I should not ponder if/whether it was/had been her older sister.

[Tdol]

I agree with Svartnik, though I think that the past would be more common than the past perfect

[Ricco]

Thanks!
I had these sentences on a test and only one answer was correct.
Ricco