if you clip her, the coarse coat will turn soft, and the bright colors will mute. Red will turn buff, black will turn grey. Ideally, you will hand strip her, and yes, that is pulling the dead coat out. New growth will not come in until the old dead is pulled out. If you clip, only the undercoat grows back, hence the dulled colors.
Its very easy to do on a Jack, cause they are small.

You just grasp the coat between your thumb and forefinger..a few of the longest hairs. Pull the skin tight with your other hand, and just pluck the coat out. That long, dead coat will come out very easily.

The body has no pattern, so should all be one length. You can leave short eyebrows and "beard". Ears should be VERY short. If you do a search for stripping you will find many articles about it. I would recommend if you want a groomer to do it, that you find one that knows how..cause it sounds like the one you have no doesn't have a clue about it.
Just because she is a pet and not a show dog does not mean that you can't keep her nice coat. A clippered/soft coat will not repel water, burrs or mud like a coarse coat does..and soft coats get matted.