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.
If the conditions of paying zakah are met in that money after she became a Muslim, like if the money had reached the Nisaab (the minimum amount liable for zakah) and a whole lunar year elapsed on it, then zakah is due on it, and zakah is not waived because of the inability to get hold of the money. However, there is a difference of opinion among the scholars about the money that one is not able to dispose of; does he have to pay zakah on it for all the previous years, or does he pay the zakah when he gets hold of the money for one year only? The fatwa that we adopt here at Islamweb is that he pays zakah for one year only and that zakah should be paid in the same country where the money is, and not in the country where she resides.
Ibn Qudaamah said, “If a man is in a country and his money is in another country, then I prefer that the zakah be paid where the money is, but if some of his money is where he lives and some of it is in another country, then, in this case, he should pay the zakah of each amount of money where the money is…” However, if she paid the zakah in a country other than the country where the money is, then we hope that there is nothing wrong with that. Shaykh Ibn ‘Uuthaymeen said:
“It is better to pay the zakah of money in the country where the money is, as the poor covet it, and it is the apparent meaning of the saying of the Prophet to Mu'aath Ibn Jabal, 'Tell them that Allah imposed on them zakah that is taken from their rich and given to their poor.' However, if there is any benefit in transferring the zakah to another country, like if someone has to pay zakah and he has needy relatives in another country, or that people are most in need in the other country, or the people of the other country are more beneficial for the Muslims, then, in this case, transferring the money to another country for the above purposes is permissible and there is nothing wrong with it.”
As regards the debt of your wife, if she was obliged to pay the zakah and after that became indebted, then in this case she must pay the zakah and not deduct the amount of debt from the money of zakah, so this does not make her exempted from paying the zakah. However, if she was first indebted and then after that the zakah became due on the money, then she is entitled to deduct the amount of debt from the money and then pay the zakah on the remaining amount of money if it is not less than the Nisaab.
For more benefit, please refer to fatwas 87557and 116828.
Allah knows best.