Firstly thanks a lot for answering!!
She will probably use it from her house, where only she and her husband live.
Also, I think it's quite an exaggeration to say that when her IP changes, the other one who takes her IP will be able to enter. To do that he should:
-Know her site
-Know her IP
-Know that he got HER IP
-Know the URL of the admincp
-want to harm the site
Quite impossible, isn't it?
About the password, although it also seems quote exaggerated, I will try to encrypt it as it won't be a big change in the code