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 is His slave and Messenger.
It is not permissible for a woman to travel without being accompanied by her husband or a Mahram, regardless of the distance or the period of a journey. Every journey, which is considered travelling, a woman should not go on without being accompanied by a Mahram. The Prophet said: “A woman must not travel unless a Mahram is with her.” [Al-Bukhari and Muslim]
There is a consensus of opinion among Muslim scholars that the travel of a Muslim woman without a Mahram is forbidden. They differ only concerning her journey for Hajj and Umrah, or Hijrah (migration) from a non-Muslim country, or escaping from a prison.
Imam Ibn Hajar wrote in his book al-Fath: “Muslim scholars have deduced from the above Hadeeth the prohibition of a woman's journey without being accompanied by a Mahram, and they are agreed on this issue. They differ in the permissibility of her travel without Mahram only for Hajj, Umrah, or making Hijrah from a non-Muslim country.”
Everyone who considers the dangers in her travelling without Mahram such as her sitting beside a non-Mahram man, or emergency landing of the plane in any country, or its delay, or the woman herself may face illness or exhaustion and be compelled to stay at any airport etc., whoever considers all these strong possibilities, he will no doubt realize the great wisdom of the Sharee’ah in this prohibition, even if she travels by an advanced means of travel.
Know, the Islamic rulings are legislated by the One Who is fully aware of the humans future advancement.
Allah Says (what means): {Should not He Who has created know? And He is the Most Kind and Courteous (to His slaves) All-Aware (of everything).} [Quran 67:14]
Therefore, you should be patient till Allah makes your problem easy. You may find enough money to spend on her journey with a Mahram or you may find permission from your company, Allah willing.
Allah Says (what means): {And whosoever fears Allah and keeps his duty to Him, He will make a way for him to get out (from every difficulty). And He will provide him from (sources) he never could imagine.} [Quran 65:2-3]
Allah knows best.