Answer:
Isn't she?
Step-by-step explanation:
The other person is right and I'll explain why!
Both, didn't she? and doesn't she? are improper in this sentence.
Now we would have to choose from isn't she and wasn't she, for this one we will have to go back and look at the sentence.
Jane is British,
We can tell from the keyword "is" that this is present tense.
Wasn't she, being past tense can now be eliminated as an answer choice.
Leaving us with Isn't she, which you can probably already tell is present tense, meaning isn't she is the correct answer.