PCOS from a western perspective appears to be related to insulin-resistance and obesity. Being a "syndrome", however, all of the causes are not well understood and even the diagnosis itself is not definitive.
Before I start an answer I wanted to point out one thing in your post which may or may not have been intentional. You appear to be using PCOS and PCO interchangeably. It's important to know that they are not interchangeable - that is women with polycystic ovaries may not have PCOS (polycystic ovary syndrome) - 20% or so in fact do not.
You will have to see your patient first and report all of the relevant signs and symptoms for us to offer any real useful advice. As you are well aware Chinese Medicine treats patterns, not conditions. PCOS is often related to dampness/phlegm possibly with heat. Where this is coming from, however, is different for each patient and you must perform a proper diagnosis. Kidney Yang deficiency is probably the most common pattern, but other Kidney patterns, Liver Stagnation and Spleen Qi Deficiency are also possibilities.
Regardless, with proper diagnosis it is a treatable condition. The patient, however, has to be involved with dietary changes and exercise (i.e. they have to lose weight) to facilitate the required hormonal and endocrine changes that acupuncture and/or herbal medicine will stimulate.