I agree with Evelyn that this could be something other than AD.

If you do take her to an emergency room, you may need to
exercise some restraint over what they do.  Hospitals sometimes
have a protocol that they follow for a stroke and stick to it
whether the patient is a 40 year old otherwise healthy person,
or an 85 year old patient with AD, heart disease, and generally
frail health.  If they want to do something risky, painful,
upsetting or with only a small chance of helping, be sure to
discuss it with them in advance and ensure that it's something
that you think is really in the long term interests of your wife.

It might also be just the AD manifesting itself.  It seems to me
that patients sometimes reach thresholds where they can hold
things together pretty well right up to the threshold, then a small
additional deterioration puts them over the line and they can't
hold it together any more.

I can well imagine how upset you are now.  This disease is
so difficult and stressful for everyone.  I'm sure you know
that there's a limit to what you or anyone can do.  Much of it
is just out of our hands.

Take care of yourself and best of luck.

   Alan