Jo and Tim,
Have you seen birth certificates for all of your grandmother's children? If not, I wonder if they might provide a clue.
My grandmother was raised by family members with a different surname. Her first child's birth certificate lists her actual surname; my father's birth certificate lists the name she grew up using (her grandmother's maiden name).
You have your grandparents' wedding record, so you know when and where they got married. Would there have been a little write-up in the local newspaper that might provide some clues? You could write to the local library or local history society and ask if they'd look for it for you.
Have you searched for an obit for your grandmother? Maybe her sister and parents were named.
Have you contacted the funeral home that did your grandmother's service to find out what they have on file? Have you asked family members if they have the guest book from your grandmother's funeral?
If you know what religion your grandmother was, you could write to the churches in Tewksbury and ask them to search for a baptism for her. I agree with other Rootschatters that her day and month of birth are likely to be correct (although there's no guarantee it will match exactly with church records). I would mention everything that you know, including her sister named Lou Lou, whose given name might have been Louise, Louisa or Lucy.
There are still lots of avenues for you to explore, so don't give up!
Regards,
Josephine
