Hello, Mary White!
Mary Cole is correct in that you can switch the positions of the profiles before you complete the merge.
Once you click the link for a final comparison (the link that reads "You can complete this merge after a final comparison. ") of the merge, you will be on the merge completion page. At the top are 2 yellowish boxes; in the second box is a link that reads "If Dix is correct, click here to reverse the merge." You must click that link if you want to keep Dix as the LNAB (last name at birth).
I've embedded the links in my comment, so you should be able to click the "click here to reverse the merge" link to complete the switch directly. If you need help with this process, just let us know!
You don't have to be a profile's manager to change its LNAB, Fann; you just need to be on its Trusted List.
I'm not absolutely certain if that includes Family Members.