She remained in ihram because she thought that exiting ihram could only be done after tawaf al-ifadah
Question

I did Hajj this year, and because of my ignorance and misunderstanding, I thought that women could not exit ihram until after doing tawaf al-ifaadah, and I delayed tawaf al-ifaadah and did it with the farewell tawaf (tawaf al-wadaa‘). Thus I remained in ihram for all the days of my Hajj – but I did not do any of the things that are prohibited when in ihram. Do I have to do anything?
Praise be to Allah.Exiting ihram is done in two stages: 
1. The first or lesser exiting of ihram. This is attained by doing two out of three things: stoning the Jamaraat, shaving the head (or cutting the hair), and tawaf. If a person stones the Jamaraat and shaves his head, then he has completed the first stage of exiting ihram and everything becomes permissible to him except intimacy with his wife.
2. The greater exiting of ihram, which is attained by doing all three actions: stoning the Jamaraat, shaving the head, and tawaf, and by doing sa‘i for one who still has to do sa‘i.
Based on that, if you had stoned the Jamaraat and cut your hair, then you had completed the first stage of exiting ihram, and you could use perfume, cut your nails and other things that were prohibited whilst in ihram – apart from intimacy with your husband – but if you refrained from these temporarily prohibited actions because you thought that exiting ihram could only be after doing tawaf, then you do not have to do anything. The most that can be said is that you did not do that which was permissible for you. 
And Allah knows best.