Holly ****! I hate these situations. I don't know if you had trust enough this coworker to tell him/her such a thing. It's a very tough situation.
The times I was in the same situations I used to keep silence or say something to make clear that I didn't want to talk about it unless I felt this person as a friend. It's a way to safe my face but the failure feeling was inside.
I still feel very tiny when I see how my coworkers and people I meet have much more experience and interact with others much more easily than me.

With age, I'm becoming much more selective with people. I used to spend my time with people I notice that can be understanding. With others I only talk about the weather and the less as possible.

I think you can find some kind of balance. I know you find very hard to talk on the phone, but with time, it will be a mechanic activity. I hear about many avoidants who got used to the phone call in their work.
With your coworkers, the best for you is that they find you are a shy girl. They don't have to know anything else and think that, as the previous poster said, everyone wears a public face. They have also their problems, their disappointments, their flaws.