On second thought, I have no idea if this could have maybe even been done on a friend of Lyric's computer. Maybe Lyriic was sleeping over at a girlfriend's home and the girls decided to have a little fun. I think girls are bolder (and a bit more ornery) when they are together as opposed to alone.
I have to keep an eye on my daughter's computer activity pretty closely. She is the exact same age as Lyric (born in October of 2001) so she isn't supposed to even have social media accounts, but I caved in and let her as long as I am always kept as a "friend" and have her password. She will click on anything and every so often I have to go in and clean things up and deauthorize FB apps.
FB has made it very easy to create accounts with other providers because they have what is called Facebook Connect, which is a part of their Social Plugin arsenal. Service providers that extend their functionality into Facebook simply have to prompt the user to authorize the app for various functions; such as, post to wall, access friends list, access personal information, etc.... Through Facebook Connect, the service providers can even have a user login via Facebook on their own site outside of Facebook.
Since most people stay logged into Facebook when they step away from the computer (especially kids), it is very easy for anyone to use the computer and create an account with a service provider. I wouldn't doubt that Misty created the Zoosk profile simply by using a computer Lyric was already logged into.
ps: I am an "expert" on anything and everything related to web - but I am not a "verified expert" so take anything I say as opinion.