If you are grandma's tenant, then SHE will have to pursue any eviction action through the courts. You would appear to lack any standing to do much of anything other than, maybe, assist your grandmother.
This sounds as if it might be a sublet situation which can get a little more complicated if your roomie wants to make an issue of the whole thing. You can go ahead and try to issue the notice and work towards an eviction, just understand that if you cannot gain voluntary compliance to leave, you may have difficulty pursuing a kickout order in court as a tenant yourself.

