The Other World at first ...
When Coraline first enters the other world, the Beldam had created it to amaze and impress Coraline. She did this as she wanted Coraline to love it so much that she'd let buttons be sewn into her eyes to stay. The world is beautiful, colourful and wonderful. It seems like magic for Coraline and, at first, she becomes keen to go back to the other wold to escape her own boring one.
and after...
Though after Coraline starts to suspect the Beldams plans ands attempts to escape the world, things turn sour. The Beldam transforms into a skeleton-insect like creature and is no longer the loving, sweet and happy mother. She plots to trap Coraline in the other world, forever.