I have carried out all my research for Rebecca on the Internet. I know the IGI is pretty thorough with its info although I know some info is missing. I've tried everything to find Rebecca which has made me think she might have been married to a Bird.
I have found a Rebecca Onions married to Henry Bird in Wellington on 22 April 1793. There is also a child, Mary, baptised in 1794 in Wellington. Was Henry much older and was he from Shifnal? I cannot find a baptism for Henry in Wellington but there is one in Shifnal in 1753! There is a baptism for Rebecca Onians in Wellington in 1774.
This is just a theory, but there are Onions and Bird(s) in Shifnal so there could be a link between the families in Wellington and Shifnal, there is not a huge distance between them. Rebecca is claiming to be born in Shifnal in the 1851 Census - maybe she was but then baptised in Wellington because of family links there. (My son was born in Hertfordshire but baptised in Yorkshire where my parents live!)
So, I'm wondering if it would state she was a widow or spinster at the marriage to William Glover in 1796 at Shifnal? Is there a death for Henry Bird between 1793-96 at Wellington or Shifnal?