For starters, we do have a workshop on it in the lessons here:
BPD BEHAVIORS: Silent treatment - verbal abuse.In answer to what can you do? Not as much as you would like--you cannot make her talk to you or acknowledge you.
Your best bet is to find something that you will enjoy without her... .and do it.
The other useful thing I do is occasionally offer a kind greeting or offer of something nice, perhaps a cup of tea or something. In an open and friendly but not pushy or demanding way. Although only when I'm feeling grounded and content.
The reason I do this is that the silent treatment can be one of three things regarding you... .and it can be hard to tell them apart:
1. Punishment for something that she feels you deserve to be punished for.
2. Her recognition that she is in such a horrible mood that she would only hurt you if she did interact with you, and an effort to spare you of that.
3. Reason #1 or #2 is gone now, but she's still not talking out of inertia or embarrassment at what she was doing.
Reaching out won't do much damage in state #1 or #2, but probably won't do much good. However if she has made it into state #3, a friendly touch is a wonderful opportunity for her to return.
How long has it been this time?
GK