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You've been watching too many spy movies.

Keyloggers are installed by malicious software that you unwittingly downloaded, not by some ninja hacker sneaking into your house when you aren't home.

Run something like malware scan on your machine to see if you even have a key logger. Or, if you are truly paranoid, wipe the hard drive and reinstall the OS anew. That will get rid of everything. Literally.
 
Why do you say that? There are legit keyloggers that people can purchase to monitor, say, their childrens’ web habits. It’s not entirely far fetched that this person could have installed one on my iMac. I’m just not sure if she would have needed my password to do so.
Unless your Mac was left unlocked and unsecured, there was nothing installed.
 
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