Jan Fennell is a very outdated dog trainer and isn't highly rated anymore in the dog training world. Her methods are all based on dominance/pack leader theory, the idea that dogs will behave as long as they see you as a dominant pack leader. This is a flawed theory which has long been disproven - modern studies have shown that dogs don't form wolf-like packs and are not striving for dominance. Her "Amichien bonding" technique advocates using things such as always eating before your dog does, right from puppyhood, as apparently this is what happens in the wolf pack and shows you to be the leader - it's not, though, in any pack the pups always eat first as they are the next generation and are the priority. Such techniques are pointless.
She doesn't have much concept of how dog behaviour actually works. Her methods involve the use of VERY harsh techniques which involve sudden and protracted periods of ignoring and shunning the dog (which creates confusion and depression) and insisting the dog 'earns' practically everything it wants. It can seem to work, generally where the dog previously had no rules or boundaries and now there are very rigid rules and boundaries. Unfortunately this can come at the price of the dog being depressed and shut down. For some people, a very flat, depressed, shut down dog can appear to be an improvement over a bouncy mannerless nutter!
Please also avoid Cesar Millan type techniques. He is an awful dog 'behaviourist' for a variety of reasons. And avoid squirting her with water or citronella squirt collars - these often offer short term quick fixes but can do long term psychological damage.
Unfortunately, as with most things, there is no quick fix - clicker training is probably your best option. Maybe look at the 300 peck method, many dogs are successfully taught loose lead walking using this method. http://www.druidalegsd.karoo.net/300peck.htm