I am currrently receiving treatment for breast cancer, and would second everything already suggested! Bear in mind she might have times where her appetite or sense of taste is affected once she starts the chemo, so you might need to wait and see what she fancies in terms of food. My doctor told me to eat what I fancied, cos it would make me feel better! When my taste is affected (it comes and goes, depending on where I am in my chemo cycle) I usually fancy strong tasting things e.g. Salt and vinegar crisps, as I can actually taste them.
my sister sends me hand made postcards, with positive encouraging messages on, to remind me that she is thinking of me. I have put them in a small photo album and look at them often, especially when i am having a crappy day. She also sends silly things she's cut from magazines, daft pictures, just anything to make me smile. A good friend also sends me random things in the post. I never know when or what, but they always cheer me up. She has sent me a flowery coaster, a small padded heart, a knitted flower brooch, a teddy bear and a bar of chocolate.
For me, the hair loss thing was not a big deal, but still a shock when it happens. However, once it starts to go, it goes pretty quickly, and once its gone I got used to it sooner than I thought. If she wants to use head scarves, I use Buffs, which are very comfortable, not too bulky (a problem I found with a lot of scarves I tried) and easy to wear.
You sound brilliant and I know that your mum will appreciate whatever you do for her. Facts are good, but avoid Google. There is so much out of date stuff, it doesn't give a true picture of treatments etc. Use Macmillan site, or Breast Cancer Care website. They are considered the most up to date.
Will post again when I think of anything else. Big hugs to you and your mum x x