Recognition human in images through HOG descriptor and SVM classifier performs poorly
You are using the training set that opencv is giving you which it doesn't correspond to the kind of images you are using. The data you are using comes from getDefaultPeopleDetector and the kind of images that the default detector uses are pictures of many people, not a female model from a fashion ecommerce. 

If you want to distinguish between models and garments you can try to train your own classifier with HOG or other features. 

Another path you can take is to detect if there is a face or not. You could use haar cascades for that.