keep moving.

if you double jump late you should be able to dodge the red homing attack and also, keep your distance because her physical combos are powerful. usually if you move away from her while she's attacking, the combo will miss. on low health, rosso's combo becomes much longer but its just as easy to dodge. the bullets will be easily avoided if you just lock on and strafe left or right.

try to move sideways and backwards at the same time so you stay at a safe distance while fighting so that way, if rosso speed at you to do a combo, you can see it coming and dodge.

there is also a vending machine where you fight her so you can buy healing items.