Spend time with her while you can. Please don't give yourself the opportunity to regret not doing it. I understand that it can be hard, but you'll be thankful later that you had the chance.
My father was taken last year after suffering from Alzheimer's for several years. A year or so after he had enough symptoms to be diagnosed, he became nonverbal and a shadow of the person he was. My advice is to spend as much time with her as you can before it gets worse. By the time I realized how bad things had gotten, it was too late for me. My father could not carry on a conversation.
I'm sorry you have this news weighing on you. It's not something I would wish on anybody. Take care of yourself and all the best to you and your family in this difficult time.
Really sorry to hear it. We lived with my mom for the last part of her Alzheimer's battle ("battle" being the wrong word, there's no fight). It's a terrible disease and in sorry for your family.