My question would be what is the client doing (or what had they been doing) that lead to the issue in the first place. Remember that you are focusing at the moment on symptoms but these should only be used to understand the cause. To many symptoms are just going to confuse you. Let's work backwards a few weeks or even months to see what she might have some tendinosis/itis of the proximal hamstring. And which hamstring at that? This type of thing doesn't come on by sitting on a chair. The lateral issues on the knee could indeed be related to hamstring dysfunction (and therefore the lateral joint line) and or proximal tib/fib issues. But yet again we must consider the lower limb biomechanics to see what it is that she is doing that is resulting in her problem. Does she have a rotational instability (ALC or PCL issues) in the knee. Please do share this information.