From Jiuzhaigou to Siguniang Shan

I need to get from the valley to Siguniang Shan (or Wolong), is there a direct bus? What is the cheapest way? I read that I need to come back to Chengdu and then take another bus from there, but like this I will waste money and time I guess.

Can you help me please?

Thank you in advance!

Flavia