me thinks too many questions and too little info provided hence no replies
As your housemate needs quite a lot of information it might be best if she paid a visit to her local Citizens' Information Centre and they should be able to help. She could also give them a call if she can't visit PHONE 021-4521600
The current rent of €400 exceeds the maximum rent limit for a single person in shared accommodation anywhere in the country. In general, this would exclude her from Rent Supplement, but exceptions can be made if there is a risk of homelessness.
There are also different qualifying rules depending on whether the tenant lives in a HAP (Housing Assistance Payment) area or not.
She can apply for a medical card, her income and outgoings (rent, travel costs to work) will be taken into account.
More information on the Medical Card, including the income guidelines, can be found here http://www.hse.ie/eng/services/list/1/schemes/mc/about/Amieligible/