Wow, those are some intense levels of color. Not my preference, but if it works for her...I won't tell her (or you) it's wrong.
As mentioned, that is largely don't in post...but there is a lot more to it than that. It probably starts by choosing the colors that are there in the first place...so what the subject are wearing, the backgrounds etc. Another factor (the most important factor in all types of photography) is the lighting. Whether it's creating your own lighting, or knowing how to best use natural light...you can't create great photos without great lighting. In other words, you can't just take any photo and punch up the colors...you still need to have good lighting techniques.
As for the lens...it may be a factor. High quality lenses tend to produce higher quality images (provided the photographer knows what they're doing). Using your 55-200mm lens at 55mm, is not the going to be the same as using a 50mm lens (or your 85mm lens). That is lower quality zoom lens, especially if you use it at the maximum aperture. Prime (non zoom) lenses will typically give you better quality for the price, because they designers didn't have to compromise the quality for the sake of zooming.
The specific lens(s) that you choose to use, will depend on many factors. How much room you have to work, is usually one of them. It's usually better to shoot people with longer lenses, provided that you have room to back up.