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 this woman worked in a interest-based bank without knowing that this is prohibited, or she was deceived by the statement of a scholar who holds that working in an interest-based bank is permissible, then the most likely correct view – and Allah knows best – is that she may benefit of the money which she earned from this job and is not obliged to get rid of it. However, if she worked in the bank while knowing that this is prohibited, then she has to get rid of the money which she earned from this prohibited work by spending it in what benefits Muslims.
Shaykh Ibn ‘Uthaymeen when he was asked about the repentance of someone who worked in an interest-based bank, said:
"I believe that if this person did not know that this work is haraam (prohibited), he is entitled to all his past earnings and is not required to dispose of them. If he was misguided by the fatwa of a scholar that such work is not haraam, then he is also not required to dispose of anything. Allah, the Exalted, says (what means): {So, whoever has received an admonition from his Lord and desists may have what is past, and his affair rests with Allah.} [Quran 2:275] However, if he was aware of the prohibition in this regard, he must get rid of this unlawful money by giving it in charity (to the poor and needy), by building mosques, repairing roads, or the like..."
Please refer to fatwa 85917.
Allah knows best.