“Mentee,” used to mean someone who receives mentoring, is a horrible word. Please don’t use it. It makes no sense. You can’t “ment” a person. No one is “mented.”
It is also pretentious. I know how weird it is for me to accuse something of pretension given what I am about to say, but it makes the speaker or writer look like something even worse than a pedant, which is an ignorant pedant. The use of “-or” or “-er” to mean “one who does something” comes from Latin. And using “-er” to mean “from a place,” as in “New Yorker” is a Germanic construction. But “mentor” comes from Greek, which is neither Latinate nor Germanic. And “mentor” is not even a verb in Greek; it’s a proper noun. Mentor was a guy in the Odyssey. If you really insist on using “mentor” as a verb (and I’m not entirely opposed to that) then it would probably be better to refer to “mentorers and mentorees.” Please don’t do that either, as they are both ugly.
In place of “mentee” use protégé, student, disciple, acolyte, padawan, grasshopper, or anything else really, as appropriate. I’m not saying we should have extradjudicial executions, but if we did, then anyone caught using the word “mentee” should be summarily executed.