Girl bye. Only Get Right and maybe Love Don't Cost A Thing meet the citeria you say. All the rest are sung by Queen Ashanti/ C. Millian / demo singers, with no J-lo at all, so stop it. But i didn't expect less from a J-lo fan.
People have edited all of these tracks and she's singing as a back-up. Put your facts together, besides it was the trend back then.
Pure fan fiction, the chorus is clearly just Kylie.
Listen to the chorus sis , Kylie is not the only person featured on it, if you listen closely you'll hear Britney on it as well, so it's not pure fan fiction if Britney's vocals are on it.
The Turn Me On demo is extremely similar in parts to the final song so I'm sure they left some of Ester's vocals in. I'm not sure of Right By My Side though, I've never noticed.
Toxic: Cathy Dennis
Break The Ice: Keri Hilson
Gimme More: Keri Hilson
Piece of Me: Robyn
Womanizer: K.Briscoe
Circus: Claude Kelly
Hold It Against Me: Bonnie McKee/Myah Marie
Perfume: Sia
You can hear all of these people quite obviously on these singles. I don't think Britney's fans look to her for outstanding vocals though.