Can you name some female singers that sing low songs?

After so much trying, I realized I just don't have the high notes in
my range at all(at least for now) and I need some new songs, pretty
much pop, country or rb.
I can sing a lot of Taylor Swift songs, Colbie Caillat, but not big
singers like Leona Lewis, Christina Aguilera etc.

I can't even hit some high notes in falsetto. How can I add more power
at least to the notes I can hit? I also can't hit very low notes.

P.S. I can't take voice lessons. I'm 15.