Nowhere in the RootsMagic 6 Help system can be found the non-word "sharee". So RootsMagic did not introduce the term.
Google searches on terms involving combinations of "event", "fact", "role", "principal" with "sharee" invariably turn up, at or near the top of the results list, hits from the RootsMagic Forums or from the RootsMagic-Users List archive or from SQLiteToolsForRootsMagic, not from genealogy software features, descriptions, documentation pages. There is one hit from a Legacy page but it is a user comment. So we are the worst offenders in using this non-word.
Unfortunately, there is a patent application for sharing an online order cart which makes extensive use of the non-word "sharee" and does so in the (in my view) wrong sense. But there is no other formal usage of the word in relation to "sharing" to be found.
There are many hits for Sharee'Ah, an alternative English spelling for Shariah, as in Shariah Law, and for both surnames and given names "Sharee".
Stopping its usage now in discussing shared events should not confuse anyone because we should be using language that is more accurate such as "sharer", "principal", "witness", "non-principal", "secondary role", ...
Stopping its usage now should not be very hard. No formal RootsMagic documents use it; don't start.
Internally, the RootsMagic database identifies the Principal of an event or fact by the field OwnerID in the EventTable; other sharers in the event are identified in the WitnessTable by the field PersonID. Awkwardly, "Witness" itself is a common role name amongst all the role names for all fact types. Nonetheless, no "sharee" there and a justification that all non-principals are "witnesses".
As an advocate for clarity and disambiguation in writing, I see no alternative but to argue for the elimination of the non-word "sharee" from the lexicon related to "shared events". Please, let's clean up our act.