I wouldn't do it that way myself. Elizabeth has a good source for the name, and the only source listed on the profile is a user-submitted Ancestry tree with a now-broken link. The tree has likely been taken down by the user, or possibly it's private. Whatever the case, the link leads to nothing.
I suspect that "Bertha" is a transcription error, perhaps made by the person who submitted the tree to Ancestry. I would suggest contacting the PM with the source and getting the first name corrected, rather than adding the correct name as a nickname and leaving what I assume is an error in the first name field. If the PM has better support for Bertha, that can be looked at. Otherwise, I'd change the first name.