Apart from that index entry (which, as an index, is just a 'pointer' to how to get the record to see the details) do you have anything that confirms this is the correct Margaret Jane Johnson?
Free BMD, Search marriages
Johnson, Margaret J
date range 1881 - 1891
to start with limit the search to the county of Northumberland (got to start somewhere!)
5 results (including the one who married James WILSON)
You need to look at each one, click the page number to see the possible spouses, search later census returns to see if you can determine which male on each page married which female. Find the one that particular Margaret Jane Johnson married, check her age and birth place to see if she is possible or can be discounted do that on all later census returns you have access to to see if the info is consistent
Its a long slow process, but apart from buying all the certs its the most likely to possibly find what you are looking for.
Marriage locator
http://www.marriage-locator.co.uk may tell you where these marriages took place - as long as it was an Anglican venue.
If you draw a blank in Northumberland you would need to repeat that original search country wide, throw a double six and start again.
Busy weekend here, so I don't have time to help you search, but let us know if you manage to confirm /discount any and when I have more time I'll take a look.
Boo