You are dealing with the fundamental psychological make up of this student so you have to tread lightly, move slowly and only do so with the person's explicit permission. What approach you take will depend very much on where you are in the world.
Journal writing is a good place to start. Begin with innocuous assignments like writing about best friends, pets, food, very pedestrian topics. Gradually introduce specific topics like an exploration of this shyness or lack of confidence.
Next introduce some out-of-class assignments like calling a recorded message for things like movie times, restaurant hours, horoscope and the like. Skype is cheap enough for placing overseas calls to do so if you happen to be in an EFL situation. Keep up the journalling as well as it's an important conduit for communication.
Next, with mutual agreement, assign similar tasks where she has to talk to a real person, possibly first by phone, then in person. An ESL situation is easier, of course, but many large cities will have grocery stores, restaurants, book stores and the like catering to English-speaking clientele. Assign simple stuff like going to a grocery store and finding out if they have capers and what aisle they are in, for instance. Pre-teach the language requirements. Do this kind of thing often enough and she'll get used to it, look forward to it even.
The next step might be participate in text chat online, then work towards a voice/video chat. From there find a situation where she can have a slightly longer face-to-face with someone. Don't accompany her. She has to get there, or not, by her own volition. Task her, for instance, to visit an art gallery, find a picture she likes, ask about the meaning -- easier in a private gallery -- then debrief in class. A smartphone pic of the object d'art is helpful but not always possible.
This not a project that you can start on Monday and wrap up by the weekend. It took her how many years to get her to where she is today? This will play out over many months with set backs along the way.Brian Grover