Mazal tov on your upcoming marriage!
There is no need for the mikvah lady to see you naked. If you want her to check certain parts of your body (your back, nails, etc.), you can keep your towel or robe on while she does so. As you mentioned these checks are not required, so if you are uncomfortable with that you can tell the mikvah lady that you checked yourself thoroughly and do not need her assistance. You can then request that she look away while you enter the mikvah water (mikvah attendants usually do this without being asked). Once you are in the water up to your shoulders, she can watch you fully immerse and confirm that all your hair went under. It is difficult for her to see anything clearly when your body is under the water, and you can swish the water around to make your body under the water even less visible. Most mikvah ladies turn their back and hold up your towel for you as you come out of the water , but you can clearly state your wishes to be certain. You can mention to the mikvah lady your concerns, and likely she will be happy to accommodate you.
Please feel free to get back to us with any further questions.
B'Hatzlacha!