I can't believe the 'either' option is posting so poorly, when it is correct! Either of these can be used, depending on the sense.
I would say 'was' because it's she SAID. I would use, she 'is' for she SAYS she is from Japan. That's just me.
I completely agree with penny58...
The thing is, they both sound right; especially when you use the first and last half of the sentece with each option. And becuase they both sound right, they both sound wrong. If you say "said", you are inclined to make the rest of the sentene past tense, and thus use "was". "She said she was from Japan", then that means she used to be from Japan but now she's not? It makes no sense. But using "is" doesn't sound right because the sentece so far is past tense.
i think it could be both cause they both make since.
I too agree with Penny58. Either can't be a choice.
Either can be used. You can say "She said she is going to the party" - which uses past and present tense in the same sentence. Both are correct.