Do I personally believe that Warner Brothers is launching a new Supergirl film? No. If they were looking to reboot a Kryptonian, it would be Superman, and at this point there's no forward momentum on new Superman movies. Hollyscoop's unnamed source sounds like internet rumor-milling at its most obvious. Swift has the right look for the part, but any fanboy worth their salt can play "cast the superhero" all day; it doesn't make it a reality.
If cast, Swift would be filling in the red boots once worn by Helen Slater in 1984's much-maligned live-action version of the DC Comics character. You can watch the trailer for the original Supergirl film after the jump.