Lodgers have very few Legal rights.
Your friend will have had a verbal agreement with this woman but can choose to evict her for any reason.
Your friend has already given her notice to leave but then he let her stay.
So he needs to give her another notice to leave, after the notice to leave comes to an end, if she will not move out, at this point she is trespassing and the Landlord will be able to evict her peaceably I.e. Changing the locks while she is out.
Do not threaten or use any physical force as you may be committing a criminal offence.
Under no circumstances let her back in the house, pack her room up and have it in bags at the door, to hand to her, if she causes problems, you are within your rights to call the Police.
Give her a reasonable time, say 14 days to move her property out of his garage, otherwise you will despose of it.