Unfortunately, or Fortunately, they can only work with stuff that you have put in the home or is already there.

Now, they can buy it, send it to you, then you can place it, they can move it around.

From the UESP:

Settings - This screen lets you manage your permissions for visitors to your house. In the General section you can set the house to be your Primary Residence (necessary to allow other players to visit when you are not at home) and also set the default visitor access. "No Access" means other players cannot enter your home at all. "Visitor" allows them to enter the house but not move items (though they can still do things like turning lights on and off). "Decorator" allows other players to move items around in your house. They cannot remove or add items, though they may place them where they are difficult to find without the "Retrieve" menu, so you should only grant this access to people you generally trust. (It is highly advised to keep the default at "No Access" and only allow specific friends or guilds to have access.) The other sections let you add or ban specific players or entire guilds. Once you have these set up for one house, you can use "Load Permissions" to apply the same settings to your other houses.

She should have bought the statue as a gift, assuming it wasn't a daily reward. Because that is the only way crown store items can be traded.