A very easy way to do this is by putting the game difficulty to veteran and playing through chapter 2-1 until you can across the big man majini. Once you find one take all of Shevas weapons away and shoot him in the head until you can start the combo, sheva will do her part and then you can put the final hit in.
ADD ME ITS VERY EASY, EQUIP GRENADE LAUNCHER AND HIT JILL WITH FLASH GRENADES TO MAKE HER EASYER TO SAVE, MAKE SURE YOU BOTH GOT A SHITLOAD OF 1st AID SPRAY.
I suggest you play through the level until you get to wesker, hit him with a rocket then he goes instantly, let jill kill you once then switch equipment to grenade lancher and lots of flash greande ammo.
