a couple of points...
The cost basis would only be FMV at transfer if i that value is less then the cost basis of the owner.Otherwise it would be her cost basis. If it was owned by both your parents she might have received a step up in the basis when she became sole owner.
There should have been a gift tax informational form done in the year of the gift but if the estate of the owner at time of death was under estate tax limits(over 5million indexed for inflation) there will not be an estate tax.
If the home was transferred but left your mother with a life estate where she lived in home until her death then your cost basis might be the value at the time of her death.
Disclaimer: Not a tax professional. Information gathered from internet links. Anything dated in June 2019 was posted in prior years and is before the 2019 limits and changes.
