Dual citizen transferred to US, want to gf to live with me

The provision for retaining I-94, while it may allow someone to keep the B I-94 (as it does for a host of other classes - but I doubt B), no POE would accept its second use.

We are talking 'B' here.

I'm not sure if they issue you a new one but the principal is that you keep it and you're allowed the remaining balance of time:

In general, if you have been admitted to the United States under most visa classifications if you take a short trip (30 days or less) to Canada or Mexico, you may retain your I-94/I-94W, so when resume your visit to the United States you are readmitted for the balance of the time remaining on your I-94/I-94W.