Actually, she wrote that it was ok to have it in the church as well. Sister White encouraged the practice of putting up a tree, even at the church, to be used to gather donations by pinning them onto the branches.
While I do believe that Ellen White fulfilled all the requirements of being a true prophet and that her writings were divinely directed, I do not believe that she was given all the light the church would receive. The above quoted passage from Adventist Home shows that she was not given light in at least two areas having to do with this time of year, one being the egregious use of the term 'christmas' and the satanic meaning of the word.
Also, the decorating of the tree is in direct contradiction to this passage in Jeremiah
Sabbath blessings!