The spelling 'Riuva' is likely due to a miss-hearing; it could well be Rivka or Rifka.
Have you looked for other persons with the surname Levine living in Northern Ireland in the early 1900s, in the town (or towns) where your great grandmother lived? It is more than likely that she lived with family when she first came to your country, and probably lived with family up until the time she married. Just be aware that Levin/Levine is a common Jewish surname, and not all persons with this name are related.
The record of a Rivka Levin born on June 6, 1895 - I would get an image the original record (whatever it is), to see if there is any more information on it that might be useful to you.
As someone else above mentioned, there is always DNA testing. If Rivka had siblings, the great grandchildren of those siblings would be third cousins to you, and some of them might show up as DNA matches, if you and they test at the same company.
Lak/Lok/Liak/Lock and Kalon/Kolon in Zagare/Joniskis/Gruzdziai, Lithuania
Lak/Lok/Liak/Lock in Plunge/Telsiai in Lithuania
Rabinowitz in Papile, Lithuania and Riga, Latvia
Trisinsky/Trushinsky/Sturisky and Leybman in Dotnuva, Lithuania
Olitsky in Alytus, Suwalki, Poland/Lithuania
Gutman/Goodman in Czestochowa, Poland
Lavine/Lev/Lew in Trenton, New Jersey and Lida/Vilna gub., Belarus