Excellent point, Lucky!
The web designer may be hesitant to give give her access because of the damage someone could do to destroy the site. If he did give her access he should let her know that if she messes something up, there would be a cost for him to repair it. Of course, he should have a complete clone/backup of the site in case of problems.
However, the designer should either be able to handle it from anywhere in the world, or have someone to handle it while he is unavailable.
It is critical to maintain control of your website.
Bad example - - a friend wanted to make minor changes to her website.
She did not have the needed passwords.
Her web designer refused to give her the logon info, saying he would take care
of it when he gets back to town. WHEN??
Of course many web designers don't operate that way, BUT it points
out why it is critical to maintain control of YOUR website.