倒れた原因はおそらくお腹がすき過ぎたことと緊張感が極限に達したためでしょう。 I think the cause of her fainting was being too hungry and too tense.
カナダに来て食べた食事が合わなかったために胃がもたれ、神経質になってその後の食事が満足にのどを通らなかったようです。 It looks like Canadian food doesn’t suit her and made her stomach feel heavy. That must have made her nervous so she couldn’t eat properly.
一人旅で、言葉を助けてくれる人もいないので、ますます緊張したんですね。 She was traveling alone and she had no one who could help her with her English. She must have gotten more and more nervous.