My mother wrote a will but several years later she wrote me a letter stating what is mine after she passes. Which stands the will or the later dated l

The Will is the governing document and will trump a separate writing. That said, a Will oftentimes contains a clause that refers to a separate writing where the testator (the one making the Will) leaves certain items of personal property to designated persons. This writing, however, is not binding on the personal representative (i.e., executor) of the Will.