Elderly person needs to move into AL but not advised to because of bad short term memory loss. What to do?

I can be hard on a person with dementia to move to a new environment. But sometimes it is the best solution anyway. (And sometimes such people don't recognize where they are when they remain in their old homes.)

Do what has to be done, and ask the staff for ways to make the transition less scary.

A good facility will either assign a buddy (another resident) or a staff member to help the new person settle in. When mom first moved to the ALF, she had trouble finding her room. After a week, she finally got it OK.
She really does like the company all around her.