A friend says she can see my status on Yahoo Messenger when I am in “invisible to everyone mode”.
You can check online by type in your friend yahoo name at http://www.ydetector.com/
Download and run Detect Invisible Me and find invisible Yahoo contacts one by one .
Online checkers Hotmail \ Yahoo http://blockstatus.com/msn/stchecker
if your friend is using a third party chat app, then it may be so that she is able to see your status.
For ex. http://www.trillian.im/
if you have it installed you can link it to your social accounts and see who is online
no way you can not but yes create another account add your contacts and you can monitor them from the second account :p its really handy