'Depression' is becoming a catch all diagnosis so they're no way for me (or anyone else here) to know if your daughter needs medication. Teenagers are often moody and it's partially due to all the hormone changes. Most teens grow out of it when their hormone levels stabilize and they don't need medications.

Chemical depression is different from being depressed because of tragic events. The result may be the same but the root cause isn't. Chemical depression can't be handled just by talking to a therapist. It may be helpful to speak to a psychiatrist but it won't fix their chemical imbalance any more than talking to a therapist will cure cancer. If the body isn't making a chemical or not making enough, all the talking in the world isn't going to fix the problem. Depression caused by a chemical imbalance won't go away unless the body begins making the chemicals in the proper ratio or medication corrects the problem.

Your daughter needs a complete physical. Whether her depression is mental or physical, a chemical imbalance needs to be addressed or ruled out. If it is a chemical imbalance and the doctors can determine which chemicals aren't being produced in the proper quanities, then medicine will make a remarkable difference. It might make such a difference that it's all she needs.