Cyclist attacked

What defensive/self protection measures are legal here? I'm a Yank, so it's an honest question. I carry my D-lock on my waist but I'm not entirely confident in using that against a group and I'm more interested in something for my wife to carry when she rides.

First rule of self-defence is get the hell out of the situation if you can.
If you start waving stuff around you'll aggravate the situation.
Saying that, if they're already laying into you I'd d-lock as many of them as I could.