Is your groomer hand stripping, scissoring or clipping? Whichever she is doing will make a difference to the finished look. When you arrive please make sure you have a good talk with the groomer so you can decide what you want done and that the groomer knows too, as some groomers seem to think that all Cockers should be fully clipped and have no feathering at all. If that's what you decide, that's fine. But if you want something different you need to make it clear to the groomer. If you can find a picture of a Cocker looking how you want Tessa to look you could take that with you.
Something else to consider is that it's the first time for Tessa with a groomer and you want it to be a pleasant experience and not too long or stressful. So you might just want her to have a bath and a tidy up of paws, legs, ears and top knot. Is she used to being combed and detangled by you regularly? If not, the whole process will take longer anyway and may be more stressful. A good groomer will listen to what you want, or guide you if you're not sure, but will also want to keep Tessa happy and calm.
Hope it goes well and you have some nice photos to post later
