Dont tell her.
If she is on an extended holiday she may be trying to "get away from it all" (including the problems with her mother).
If you DO tell her what can she do, just WORRY about it.
Let her enjoy her break.
If she knows about the suicide attempt then the death of your mother (when it happens) wont be a surprise as years of alcohol abuse can cause the body to "give up" at any point.
(My first wife was an alcoholic and one night went to bed as she felt a little unwell, and died in bed. The body just cant take the years of abuse).
I repeat, dont tell her.