Cost Basis on Inherited Rental

What is my cost basis on a rental property that I inherited half of in 2022? I owned the property half/half with my mother who died in Oct 2022. We purchased together in 04/2021 and split everything when she was alive.

I had a CPA do both of our 2022 taxes last year because of the split/death/trust etc. I noticed that the CPA used my cost (only my half) as the cost basis. I don't think that was correct. The property was not in the trust.

TIA, Chris