First off perhaps you could change the title of the thread to ' Recommend a solicitor for a probate case in Northside Dublin?' to obtain some relevant replies- I'm afraid I don't know anyone to recommend.
Secondly it may very well be that your friend's brother IS entitled to half the house and if so, to live in it. However if for example your friend was living in the house with her mother, taking care of her, paying bills because she had been promised that the house would be left to her, then she may have a bigger claim than just half the house- I say this because of the mention of an unsigned will ( presumably in your friend's favour). A good solicitor will go through the background with your friend and will be able to advise accordingly.