Black or tarry stools can often be a sign of intestinal or stomach bleeding, this can be a symptom of many serious problems, and also of some not-so-severe problems but she should definitely see a doctor and have tests done just incase.
It might help settle the stomach for her to cut down on the alcohol as it's been known to cause diarrhoea, particularly the next day after a big night on the grog, but it seems doubtful that this is the sole cause, merely a possible contributing factor.

There are products available over the counter in pharmacies that can help dry up the stools and reduce the frequency of the diarrhoea, such as loperamide hydrochloride, which is sold under many different brand names. however it shouldn't be used if there is blood in the stools without first talking to a doctor.

Thanks cabbageman for your advice.Yesterday my neighbour was in a bad way but she still wont see the doctor or do anything about her been unwell,she got very nasty and said she will be alright beside her was another bottle of sherry so theirs no way she is going to cut down the alcohol so what can i do to help her?
.Other symptoms are yellowing of her eyes itchy skin swollen legs after doing some reserch i belive she has liver failure.Been 9yrs of heavy drinking since she lost her husband although she seems to be over her loss she has stuck to her drinking.If you have anymore advice it would be much appreciated.Sharon x