Mac keyloggers?

I know it is possible for macs to get keyloggers, but I'm wondering if its possible for someone (an acquaintance, not a website) to download a FREE keylogger on a mac by accessing the computer.

I think my sister may have put a keylogger on my computer, but before I start stressing out I want to get the facts.

I know she wouldn't have purchased one, so it would have to be possible to download for free, and I am unclear or not as to wether she has the administrators password. Could she have put a keylogger on my computer?

If so, what can keyloggers detect.. can they really detect EVERY key typed (such as emails), or just password/credit card number stuff?

Lastly, I downloaded macscan and I only saw three categories, "spyware", "cookies", and "tracking cookies". Which one of these would keylogger be categorized into,if any?

Mac keyloggers?network

Keyloggers are programs that keep track of every key you type while using your computer. This information is stored on your computer, and can sometimes be transferred to a remote attack with a trojan horse. Keyloggers can help a malicious attacker steal sensitive information such as Social Security numbers, Credit Card numbers, and bank account information.

Mac keyloggers?norton

Personally, I don't own a Mac. But from experiences of messing with a keylogger on my computer, (got bored one day lol), they track every key pressed. Some also track wich programs and what sites visited so they can tell when important information is being entered, instead of tracking every random keypress. But technically they DO record EVERY keypress. They would probably be considered spyware also.
sorry, dont know about the first two but if the computer found the keylogger it would be int he spyware catagory.