First off, congrats on losing 53lbs. That is spectacular.
I think you are taking her compliment too literally. She is saying that you've done a great job and are looking good....not necessarily that you are going to be underweight if you continue.
However, if she is indeed telling you that you don't need to lose weight, just ignore her. It is really nobody's business but yours (and possibly your Dr). Don't let it worry you at all.
And here I go, not minding my own business....but unless you are massively tall and/or muscular, at 182 you can definitely lose more weight without even coming close to being unhealthy. So carry on!