What might years of 5mg diazepam have done to my mother?

My mother took 5mg every night for an eye problem for years. She had epithelial dystrophy, with issues happening at night that could be reduced by altering her sleep architecture this way. I can go into more detail, but a lot of people are understandably squeamish about eyes.

She'd been doing this for many years when I cut off contact, which was nine years before her death, and I assume she continued. I never heard of her changing her dose or anything. She was a very odd woman, to put it delicately, as well as being abusive to me and to my stepfather.

She died early last year, and I'm now trying to sort out what's going on with her estate. It seems such a mess that I'm not sure she was entirely of sound mind when she wrote the will, although getting it overturned at this stage would probably be more trouble than it was worth. I've only just found a lawyer, so we'll see what's happening once we get hold of the estate accounts.

Does anyone know what those years of diazepam use may have done to her mental capacity? She died at 75 of cancer, for what it's worth, and made the will under two years before her death.