I think the flaws of many puat (in training) is that they forget the importance of the psychological frame of mind.
I think the value of the mind is always ignored, the mind is a very powerful organ, yet at the same time its easily controlled. What you need to do next time you go to the party is think:
" Okay these birds are fucking hot, they may think I'm a dweeb but fuck it. This is the best practice I'm going to get for a long time, I am in the social circle of these babes I am free to do what I want yet I don't have to worry about the consequences too much. GO FOR IT"
Listening to music releases endorphins in the brain, try listening to some party music or whatever gets you pumped right before you meet up with them, combine these with positive reinforcement. Don't stress, whats the worst that can happen? They think your a bit of needy person already, prove them wrong.
These are house parties, so surely theres going to be other people there that aren't in the social circle, target them? Prove that you can score girls then maybe target one of the friends when the success has given you confidence.
Search the net for some self growth bullshit. Alot of it is just that but the essence of it is the same, you define what is around you. For the basic gist I just googled "Create you own Reality" and this was the first article
http://www.selfgrowth.com/articles/Neta5.html
You said yourself, you have a routine that works, these girls are no different... they are girls as well, so if your routine works, they will not all magically be exempt.
Create your own Reality!!!
My two cents
Mildawg