Welcome to the Academy!
There are many, many helpful, knowledgable members here that would be happy to help you find an answer to any questions you might have. I know of at least three members here who have experience working with fear aggressive dogs, including myself, so you're not alone! I would recommend finding a behaviorist and/or positive trainer to help you with Jessie's aggression. Depending on the extent of Jessie's aggression, this could be a process that takes years. Don't be discouraged--my boy's fear aggression was moderate-severe, and he hasn't had any fear-aggressive outbursts about 2 years now. His fear aggression started when he was about 8-12 months old or so, and I worked with him consistently from that point on. His fear aggression really more or less dissipated after about a year of working with him. But, if varies with every dog.
Here's some great books to check out:
The Cautious Canine by Patricia McConnell
On Talking Terms with Dogs: Calming Signals by Turid Rugaas
There are MANY other books that would be of great help to you, these are just two that I have read so far. Patricia McConnell, Turid Rugaas, Emma Parsons, and Jean Donaldson are just a few great authors to look for.
But still, it would definitely help you tremendously to get the help of a behaviorist or a positive trainer with experience working with fear aggressive dogs.
Welcome to the Academy, good luck, and enjoy the site!