Lose yours, too. Seriously, take the clippers and go to town. You see the baseball teams put on their rally caps? Put your's on.
Sarah was depressed about losing her's too, after it had to be shaved for the shunts and the biopsy when we first found the tumor.
Take her out, if you can afford it, and do something "girly" for her. Nails, spa treatment, whatever.
Our neighbor did Sarah's nails to try boost her morale a bit. It helped. Not so much the nails themselves, but sitting at the desk and having fun doing 'em, being able to talk and be silly, just doing "girl" things.
Sarah wanted a hat. The Superman hat she's wearing in my avatar pic, as a matter of fact. She wanted to put the logo on and feel bulletproof, indestructible. I have one, too, I bought as a joke towards one of the shops I used to work in. She wanted to match her Superman.
Dig deep, bud. You'll get her through this. And we're here to help you get through it, too.