Anybody ever use Neurontin as a mood stabilizer?

A child Pyschiatrist put my 15 year old daughter on Zoloft for depression and anxiety and Neurontin as a mood stabilizer. Has anyone ever heard of it? When I looked it up, it said it was used for seizures and sometimes bipolar but it's not known if it's really effective as a mood stabilizer.

She has never been officially diagnosed with bipolar but she does have angry outbursts a lot over things that often times shouldn't be that big of a deal. In other words, she overreacts a lot. I don't know how much is normal teen stuff and what's not normal.

In any case, it's been 3 weeks and I don't see a difference at all. The only difference is her teachers say she seems sleepy in class and unmotivated. She still has the outbursts. I'm tempted to take her off the Neurontin. I just don't see it working at all. The doctor said I could if I want, just to do it slowly.
Should I give it more time? Or is this not the best medication to use as a mood stabilizer? Should I just stick with the Zoloft and see how she does? I'm so torn. I just don't know what to do.
Any advice?
April