I used to watch it as a kid. It was about a girl, and in her bedroom was a mirror that acted as a portal to the trolls world. That's all I really remember about it, but I'm trying to gather the movie from when I was a kid to share with my kid instead of what's on TV now.

Possibly The Hugga Bunch (http://www.imdb.com/title/tt0173915/)

No thanks though I know it was trolls and a blonde girl. But this is a good movie to show my kids!

That would be "The Labrynth" with David Bowie as the Goblin King
http://www.imdb.com/title/tt0091369/