Both can be absolutely true. An historical account can be used in an allegorical manner. There is no contradiction there at all. Gal. 4:24 is the perfect example of that where it begins, "This is allegorically speaking."
Now if you claim the account is fictional while I claim it is historically factual, then both cannot be true. Our beliefs contradict, but not the truth. One of us would be right and the other wrong in that case. To claim, as you seem to, that both are true since, after all, we believe it to be so would be sheer silliness.