First let me say that Jessica is beautiful!!, and I'm so glad you found her!!
Secondly, why are you letting your cats outside? There's nothing out there they need. You've already experienced one bad thing that comes from letting them out.
Thirdly, there are several calming products available in this catalog. Personally, I have used the Feliway Comfort Zone plug-ins, and found they work nicely - we have 12 kitties that range from 11 weeks to 10 years, so we experience the occasional spat, there is also the Calming Collar, Rescue Remedy in drops or spray, and Pet-Ease Paw-Gel. It's just a matter of what you think will work best on Jessica, and that you can administer if necessary.
I hope this helps.