That's something I've been thinking about quite a bit. Cutting the tether attached to it is no problem with the sword, but at the angle we're at now, I don't think we have the leverage to do it. If we can get her off of us, then freeing our arm from her should be a simple matter.
As for how to stop her from tearing our arm to pieces first.... I don't know. I doubt we can jerk it out of the way with it tethered; she can just jerk it back to where she wants it to be. I thought about trying to reach over with our other arm to grab it, deflect it, slash it with our knife, something. But she'd just knock it aside with one of her five other limbs.
The only hope I can see is that we get our torch into her face before her claw hits us, and that'll distract her enough to either halt the claw's progress, or knock it off course enough so that it won't do too much damage. Then, hopefully, we can get out from under her, cut the tether, maybe cut her to disuade pursuit for a couple seconds, give us time enough to try and get out of this cloud so we can breathe without killing ourselves.