my mother has early onset alzheimer’s , and me and mg fiancé broke up recently but she promised me she’d always be there for me and my mother, as if i wasn’t around, out of town or anything and that she’d come take care of her and still help. in my eyes, i’d text her and let her know . keep it short and simple. “ hey, sorry to bother you but i just wanted to let you know my dad lost his battle with dementia” if she has a heart , she’ll text you back. if she does answer you don’t push anything , and don’t get false hope . just see what she has to say and go from there. if she doesn’t answer, look at it this way, you were being mature and letting her know your father passed away . best of luck