At the end of chapter 5-3 either damage Wesker enough for him to retreat, which will give you the bad blood trophy, or wait out his 7 minutes and he'll leave normally. From here you'll need to remove Jill's device with both Sheva and Chris. This means one character has to hold Jill while the other pulls the device off her chest in the standing position.
In co-op both Sheva and Chris can remove the device, in solo only the player can do it. If you hold Jill in solo the NPC character will always attempt to shoot the device. Give the NPC a magnum or sniper and have them shoot the device a couple times. Once they have shot the device 5 or 6 times let them hold JIll and you should be able to pull off the device. This will work in co-op too but the player shooting must be a good shot or risk killing Jill