Tell her she can have the bed back but only if a few conditions are met. Those being:

Total refund of price paid for the bed,

Her arranging (and/or paying for) the moving (again) of the bed,

Her arranging (and/or paying for) the moving of a new bed of your choosing into your home.

Of course, only bring up these conditions if you truly want to save the relationship. Otherwise, just keep the bed and don't worry about it.