Shirl,here's the URL for Free BMD
http://freebmd.rootsweb.com/You need to click on search- then on the next page choose Birth,Marriage or death- or all 3 at once! Not such a good idea if you are searching for a common surname.
You can have a play about with it,by just putting in her name.
And if it gives you just far too many to search through,narrow it by a date eg Mar 1865- Dec 1886 as suggsted by Newf.
To narrow it further you can scroll down the counties and click on one of them.
Come back if you get stuck and someone will run through the results with you.
With a surname like Cooper it pretty well can't be mispelt

but you can also choose to search surnames phonetically if you have something that you're not sure of the spelling.
Have fun,
Carol