The bird is probably fine for now since it’s unlikely to recognize what a plucked bird is, but your girlfriend sounds… unwell. And needs to leave unless and until she gets herself together, lest she hurt your bird.

She's showing the bird its position in the pecking order, so to speak.

Time for a new girlfriend

OP, my guess is that GF feels some sort of competition between herself and your bird. It seems to have been an intentional threatening act of somehow asserting dominance over the bird… I agree that it’s not likely the bird understood the implied connection between chicken wings and itself so quite likely there was no harm to the bird… But GF and the relationship is flashing some red flags! I think that either she wants and expects to be above your pet in the pecking order and this was a strange way of showing that, or she is not quite mentally balanced. Be warned that if GF ever gets really hurt or upset at you, she may take it out on your bird. It’s definitely time for a relationship checkup!

When your other half is very creepily jealous of your pet, it's time to save yourself a lot of future trauma and just Nope TF out right now.