Merges can't be undone, so when this happens you generally have to create a new profile for the person who's profile was incorrectly merged away. However, in this case, I did a quick search and it looks like there are several profiles for an Ellen Newton born in 1598, as well as 2 profiles for Elinor Newton, one born in 1598 and one born in 1623.
So, to get this cleaned up, you just need to decide on a final profile ID (eg. Newton-233) for each of those two people, and merge any duplicates into them. Then (this is the hard part), look at the people who are connected to each profile. Some of them may by connected to the wrong person because of the incorrect merge. So you'll need to edit the relationships to get spouses, children, etc. connected to the right person.
I hope this helps! Let me know if you have any problems getting this sorted out! :)