@Mindy Jensen Ordinarily, there should be a step-up in basis. But, watch the paperwork!
The property is eligible for a step-up if it did, in fact, go through the estate. In this context, to go "through the estate" for a full step-up, the property had to be held by your client's mother outright (or possibly in a revocable trust).
When an heir is referring to the property as their "grandmother's" when they inherited if from their mother's estate, it is worth checking the ownership carefully. Make sure, for example, that the grandmother did not leave it to your client with your client's mother having only a life estate, or that the property was not gifted to the client rather than inherited.
(I had a client come in the other day whose grandparents gifted their home to their daughter/client's mother, who in turn gifted the property to my client. Her basis goes all the way back to what the grandparents originally paid for the home!)
If the mother was married, make sure there is not a former spouse that left their interest (if any) to a bypass trust, etc.
How to be sure? One way it to look at the property's chain of title--any gift deeds or deeds that transfer ownership to a trust?
Consider advising your client to contact a CPA or attorney that works in this area.