At this time Sylvia is a "Family member" in "pending" status.
"You get a Family Member account in one of two ways:
("Family Members" section https://www.wikitree.com/wiki/Help:Member_Types)
As soon as Sylvia accepts the invitation she should have received she is going to be able to edit the profiles she is added to their Trusted List as explained on the same help page.
"Family Members need to be on the Trusted List to edit a profile."
Hope you find helpful this information.
Before merging the profiles representing Sylvia I'd suggest to remove the e-mail address you entered on Sanders-7946 to avoid e-mail addresses conflict when merging.
When proposing the merge Sanders-9584 (ID 1) would be merged into Sanders-7946 (ID 2):
"Open" profiles are those having an open lock icon
After volunteering and signing the Honor Code Sylvia will become a full member and is going to be able to edit any "Open" profiles. To edit other profiles she has to be added to their Trusted List.
It seems the e-mail address has been removed.
In the message you're seeing when trying to remove the e-mail address "You" is not really you, "You" is Sylvia, because you're removing the e-mail address on Sylvia's profile, not removing the e-mail address of your own profile.
The e-mail addres on the profile representing Sylvia can be uneventfully removed because Sylvia is going to be logging-in to WikiTree using the e-mail address she added to the profile she created for herself.