How common is it for Alzheimer's patients to take anti-anxiety
medication?

My mother (Alzheimer's and Diabetes patient) lives in a senior
citizen complex and enjoys her apartment and the friends she has made
there. My brother lives in the area (I do not) and often stops over
(almost daily) to take her out to lunch, deliver groceries, or fill
syringes and medication pill boxes. She is used to this routine and
when he goes away on a trip she becomes anxious to the point she can
become ill. Whenever he leaves on a trip we set up coverage so people
(I cover on weekends and other family members during the week) provide
the same visitation schedule (as much as possible) as when my brother
is present. However, when mom knows my brother and wife are out of
town, she really becomes anxious and keeps asking when they will return
or who will stop over to her apartment. She relaxes only when we tell
her who will stop over and when they will stop. When my brother and
wife leave for a couple of days we don't even tell mom.

My brother is planning to leave shortly for his annual month in Florida
and we want to prepare mom and ourselves for his absence. This is the
situation that has caused the most problems in past years. She is
nervous (and complaining) the entire time my brother is gone and has
become ill during this period.

We are also noticing mother is calling my brother or me more often than
in past. Some days we get zero calls and some days she calls several
times a day. When she calls many times a day she often states "What
do I do now?" or asks the same question she had just asked 15 or 30
minutes ago. I am wondering if this is another form of anxiety.

Is there any medication that might help my mother cope with the
situations described above? Thank you for your thoughts; they are
appreciated.