My understanding of the situation --- (a) US resident taxpayer inherits a property ( abroad or in the USA? ); (b) Taxpayer then sells the said property to a Non-Resident Alien relative; (c) is this a taxable transaction ?
The gain on the transaction is computed as Sales proceeds ( which is sales price less any sales expenses) Less basis in the property ( this in case of inherited property is the Fair Market Value of the property on the day of death of the decedent). Thus if the property was not sold immediately there is likely to be some gain which is treated as capital gain.
The assumption here is that the property sold to a relative is at fair market value and therefore generally there are some restrictions on disposition on US persons but for a Non-Resident Alien buyer of property not on US soil, these rules cannto be enforced.
Note also that if the inherited property was worth equal to more than US$100,000, it needed to be reported on form 3520 -- no tax impact
If the proceeds from this transaction entered any foreign bank account that your wife either owned or had signature authority, then you may come under FBAR ( treasury form 114 ) and/or FATCA ( IRS form 8939 but not if 3520 was reported ).
Hope this helps -- if you need more , please provide more details in comments
