X turns her head to get her windpipe into the crook of Bruce's elbow, buying herself an extra second or two of consciousness.

Then she reaches for his encircling arm, grabbing his wrist in both hands and yanking down. In the same moment she lets her body drop as well, trying to use the momentum to twist free and out of the headlock.

If it works she'll try to keep her grip on his arm and twist it up behind his back.

If not --

Well. If not, there's always the claws.