There is not a specific person that is a "cat whisperer," although there are some people that understand cat behavior very well. The best way to know if someone knows what they are talking about is to first find out what their training is. Have they studied animal behavior, veterinary medicine, and veterinary behavior (this is different than just animal behavior as it does also include medications and dealing with the medical side of behavior concerns as well as medications that can be used to treat them) to name a few. You can check with your primary care veterinarian, they may have a special interest in behavior and if not, they may know another veterinarian that does. If you want to speak with someone that has proven that they know what they are talking about, then I do recommend finding a board certified veterinary behaviorist, http://www.dacvb.org/about/member-directory/, these are people that have studied animal behavior for years and have passed the tests to prove it.
A few things to keep in mind with your cats is their individual personalities. Some cats have never learned how to be around other cats and do not know proper cat behavior. When this happens and they are exposed to other cats, their behavior may be inappropriate, resulting in behavior that we do not like all around. Is it possible to keep them separated for now while you figure out what is going on in the relationship between the cats? If you have the space to do so, you can separate them into different ends of the house or apartment. Slowly start to introduce them with special treats. One of the options is to put Josie (since she is the one that chases Tinker) in a large kennel and allows Tinker to take her time to get to know her. This would only last for a couple minutes at a time. In fact, if you feed Josie while she is in the kennel and give Tinker some treats for being in the same room (even if not close to each other), they will often learn to associate each other with good things happening (being fed). If either of the cats gets too worked up, then this is not the best approach for them.
There are other steps that can be taken, but it is very important that they not be allowed to have negative interactions while you figure out which steps to take.
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