Yes you can say it is a popularity contest...which it is, but only to an extent. I think putting aside the fact that she is Rachel's sister, America likes the game she is playing. Compared to the other houseguests....
Elissa doesnt make racist or rude remarks
She is very nice and doesnt seem to purposely be mean to anyone
She is the underdog and people like to root for the underdog
So yes having Rachel as her sister helps but I think there are people who ACTUALLY think she is playing a good game.
All this being said I hope that Helen, Candice, or Amanda get it next week just for a change lol.