What characters are allowed in an Apple ID Password?

My mom has "changed" her password because she said she was asked to when logging into Facetime. Now she can't log in. When I asked her what it was, she read to me and it had both a space and a period. I don't believe those are accepted. I tried to log in from my computer 95 miles away...but no luck. And you really need to be at the computer of the log in to help. However, she is 74 so this is not an easy task. Any suggestions to find out what her password actually is so we can iMessage and Facetime?