Hitting another Pharah, as Pharah

As per title.

I am aware that these dogfights aren't meant to be engaged in because you could easily be shooting the supports behind enemy lines instead and leaving the opposing pharah to your hitscan, but sometimes there really is no way for your own team to deal with the Pharah and they refuse to switch.

In these cases where you are the only person equipped to take down an airborne target, how do you hit her?