Hmm, don't throw her into the lion's den people. Although what Benji said is technically true, it is VERY incomplete.
You do no want to start her off in the middle of a giant party filled with intimidating people as it will drive her further into her shell. Start off in very small situations mixed with known and unknown people. Go on a double date with people you have met recently. Go to a very small party where you may possibly only know the host and asked to be introduced to some people, this way you will have a lead into the conversation.
But remember, lack of confidence and shyness are completely different. Make sure your GF is seeking this help and is trying to become a more social and confident person. If you are doing this on your own, it could have an adverse effect on the situation.
If in fact it is a mutually understood confidence thing, positive reinforcement and feedback, with a helping hand in some difficult communication situations, can go along way, but again, as long as you do no overdo it.
Have her think of some things she is proud of herself for that she can use to boost her confidence in a conversation (NOT EGO though, there is a difference). And you can use those as well, for example, "did you hear my GF is applying for a position at Amazjon.jp? I think she will be perfect for this job." Put her in a small spotlight, help her answer questions when she cant, etc... But again, if you do it too much, it will just flood her with unwanted attention. You yourself need to read the situation and understand what she can and cannot handle.
All of this advice hopefully helps, and it is advice I myself have received when dealing with students in the classroom. Some students are more confident than others, and it is the teacher's job to ensure everyone is getting an equal opportunity, and you must recognize what will help whom, and who to help first, etc...
Hope it all works out.