Alsalam alykum, if me and my wife go to a camping trip at some place far where there is no one, does she still have to wear hijab or abya when she’s outside?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu 'alayhi wa sallam, is His slave and Messenger.

If you are in a place where no non-Mahrams (marriageable men) are present and you are sure that a non-Mahram will not see your wife, she will not be obliged to wear Hijab (the Muslim woman's entire dress code, which includes a veil and whatever else is needed to cover everything except the face and hands). The evidence is that the Prophet, sallallahu’ alayhi wa sallam, ordered Fatimah bint Qays when she got divorced to spend her `Iddah (waiting period that a Muslim woman observes after the death of her husband or after a divorce) at Ibn Umm Maktum’s house. This is because he was a blind man who would not see her when she put off her clothes.

The Prophet said to her: “Spend 'Iddah period in the house of Ibn Umm Maktum, for he is a blind man and you can put off your clothes in his house.” [Muslim] Thus, this indicates that if a woman is safe from non-Mahram men looking at her, she does not have to wear Hijab.

Allah knows best.