What should I do about my housemate who hasn't put her hand in her pocket for electricity and gas?

you need to address this all with her. you need a contract include a checklist of responsibilies and chores for each of you add in a responsibility list for the due dates on all the common utilities and sit down and discuss it with her. For god's sake you sign it in front of her and then make her sign the contract or tell her to simply put ..... move out.