The prevailing theory is that they did it to save on the expense of rendering her long hair. Especially since she was already defeated and captured by the time the clippers came out.

I highly suggest to anyone interested in this super hero that they check out any Inhumans comics with her, or her appearances in A-Force. Compared to the low budget show, in the comics her hair is about 50x thicker, indestructible, and so long it rolls and spills onto the floor around her.