Mary has had several depressive episodes but only one manic episode. she would be diagnosed with:

Mary suffers from type 2 bipolar disorder.

 there are  2 states of the disorder, "up" (mania) and "down". The "up", is characterized by a high energy mood, accompanied by abnormal behavior that disrupts life and the "down", that is essentially what we know as depression. In this type, the mania isn't as strong as type one bipolar disorder so we call it a hypomanic episode.

A person affected by bipolar II disorder has at least one hypomanic episode in her life but has more often episodes of depression.

Mary has had several depressive episodes but only one manic episode. she would be diagnosed with Bipolar II Disorder.