I see 5 Champion marriages in the Newtownards area in the period 1848-1864. In all the cases the father was John Champion, a painter. Robert Champion married 22.8.1851, his address then was Donaghadee; William Champion married 9.9.1848, again living in Donaghadee. Jane Champion married 29.10.1864. her address was Little Frances St, Newtownards. Daniel Champion married 15.3.1849, his address was Donaghadee. Francis married 20.9.1886. I suspect these might be Elizabeth’s siblings.
https://churchrecords.irishgenealogy.ie/churchrecords/
Mention of the Champion family here:
http://freepages.rootsweb.com/~rosdavies/genealogy/SURNAMES/C/CeCi.htm
There’s a death for a John Champion aged 73 in Newtownards in 1864. The death certificate is not on-line but you can view it for £2.50 on the GRONI site.