how to survive this meeting?

Survive? Seriously?

Step one would be to stop pretending you're going to die.

Step two is use your counting skills. You're having dinner with your gf and her friend, not just the stranger. You know half of the two.

Realize they will also talk to each other.

Have you really never spoken to anyone except your gf in your whole life?

The whole eating thing is probably something you know how to do.

You have social anxiety. I think this might affect a lot of us, especially if we aren't accustomed to being in situations such as you describe. I try doing these things in social situations:

1. Confront your fears. In many cases, introverted people like us have social phobia because we worry about what other people might think of us. What you need to do instead is focus on the two people you are with. One of the best ways I've found to overcome awkwardness is to ask open-ended questions. Try to find some common ground with the stranger. What does he/she like to do for recreation? Does he/she like sports? A favorite team? What type of work does the stranger do? How does it relate to work that somebody else you know does? Or that you do?

2. Try not to think about what this person will think about you. This may just be one meeting. Smile and do your best to appear confident. Smiling will help you relax and will get the other person to smile, also. That sets up a tone of a friendly relationship with her friend.

3. Try to think of how you feel and act around people you know. Realize that you can behave the same way around the stranger and your girlfriend.

4. Realize that the stranger and your girlfriend aren't looking for a perfect person. If you are over-analyzing your behavior, try to stop. Try to rid your mind of thoughts like: "I hope I don't say the wrong things." Or: "What if her friend thinks I'm weird?" Think of what your best qualities are as a person and also think about how those qualities can shine in a conversation with your girlfriend's friend.

5. Consider using a self-help manual and going to therapy. Get yourself involved in as many social situations as you can so that you don't feel awkward in the future.

6. Create objectives for yourself. Some of those objectives could be something like: I will not fiddle with my shirt collar (which shows nervousness). I will look the person I'm talking with in the eyes. I will control my breathing so that I'm not breathing so fast.

7. Finally, try to think positively. Instead of telling yourself repeatedly that you are going to bomb, keep telling yourself that you will do quite well when you meet your girlfriend's friend.

Social phobia is real, and it is treatable with time and practice. I find that I am less nervous around people than I used to be because I try to seek out people in a variety of social situations, such as parties, meetings, games, etc. I think you can overcome your anxiety, too, with a commitment to doing some of the things I talked about here.