I had the same issue arise, I had an account with something and they used my email address for a username so I just used the same password. She looged on to pay a bill for me or some shit and figured I used the same password since my email address was my username for both. She was right, I figured it out because she was asking questions about something that she would know about only by reading my email. Nothing bad, but I was mad nonetheless. So one day I changed my email password and she came over. I told her I needed to check my email and she asked if she could log me in. I said no, because I know you have been going in there and reading shit. She denied it, but I still wouldn't give her the new password.
Take home lesson. Use a password different from your email password for sites like that.
Take home lesson. Use a password different from your email password for sites like that.