Erm, never mind splitting the cost three ways, she shouldn't be living there at all. For one thing this arrangement with the housemate claiming benefits for the house and taking more money offf your sister sounds extremely dodgy. We had a post the other day about what we'd do about benefit fraud, and that's exactly what this is! For another thing, if they're being this unreasonable about the financial set-up, they're hardly going to be reasonable about anything else. And when your sister's coming home after a hard day's work, she's entitled to be able to relax without a houseful of layabouts cluttering the place up.

How about you buy her a nice, straightforward cookery book and a copy of the local paper left open at the properties to rent. House shares can work fine as long as everybody's there on equal terms, preferably with every tennant having a separate contract with the landlord.

Does anybody else think it was totally unreasonable for them to be splitting the shopping bill 50/50 when the housemate had a baby?

Your sister really should look for somewhere much better to stay, where her name is also on the lease, everyone is on equal footing and noone is commiting benefit fraud.
She could land herself in a whole lot of trouble if the housemate gets caught.

The housemate is most def taking the rip. Bills should be split 3 ways, except phone bill. Baby stuff bought seperately from the food. Certainly your sister shouldn't have to pay half the rent, wether you count it by rooms or how many people live there it's unfair.

Definitely not half. There are 3 of them and only one of her.
Tell them she does not want the phone anymore - she has a mobile and willl not be using the landline. If they want that they can pay for it.

I agree duboing - the rot started when baby came along and it stayed half and half.
Babies, small as they are, need milk heating, bottles sterilised, more washing etc etc.

If I was her I would definitely look for something else.