a cat and a snake?! i wouldnt say that's the best idea, when the cat is looking at the snake through the tank .. the snake in my opinion SHOULD be scared. i mean the cats preditorial instinct isnt saying hi to the snake, but dont get me wrong there are some instances where 2 animals that youd think would kill eachother become the best of friends.be careful! trips to the vet are pricey!
As for your snake being head shy.. youve only had him/her a week!!! ofcourse they're going to be shy. i know it's hard not to leave them alone because they're soooo cute but it's for the best. the last thing you want is to stress out your new pet.