Other than what is stated from the Hanafi madhhab in the Reliance, the only dispensations I have seen for a woman to travel alone are: ... - If she is a non-Muslim who became Muslim, or a slave who was freed, and or a Muslim woman escaping from Dar al-kufr. See Fath al-Bari, 1989 ed. 4:93, al-Mughni 1994 ed. 3:168, and Nayl al- awtar 4:291.
This took me by surprise, and I'm sceptical about it's truth. However, it does give references which look reliable, so there's probably something behind the claim.
Question: Are women converts an exception to the rule of travelling alone?