You’re right: you wrote “I think she’s Muslim (her parents definitely are)”, which makes it seem like you’re implying that she follows one religion simply because her parents do. Perhaps you should have clarified, then?
Again, with the assumptions and implications. You’re assuming that because Mezghan’s family “**wanted Cowell to convert”, **that Mezghan herself must be Muslim. The family could have any number of reasons making such a request of Cowell, none of which might have anything to do with Mezghan’s personal beliefs or wishes. They may be asking Cowell to convert to save face in front of the rest of their community and Muslims in general. They may simply not want their daughter to marry Cowell (for any number of reasons) and are using religion as an excuse to get rid of him, hoping he’ll refuse to convert just to marry Mezghan. I’m not psychic and don’t presume to know the personal religious beliefs and motives of complete strangers.