I want to toss my two cents in here really quick. Subs -CAN- negotiate limits with their Dom. It DOES NOT make you less submissive to have limits. I have hard no's just like anyone else. A D/s relationship requires a lot of communication, to determine every ones safe and comfortable spots. Usually it's the job of the Dom to push those limits and help teach a submissive to expand out. But, you can have limits.
I think what she was trying to say was that if you have no desire to live your everyday life as a submissive, perhaps you simply enjoy being submissive in the bedroom. There is nothing wrong with that at all.
The dynamic in the relationship of people in a lifestyle vs. bedroom BDSM setting is slightly different. But can be just as fulfilling.