Barlow,
Welcome aboard! I congratulate you and your Mrs on the decision to embark on this wonderful journey together. I am sure you will both find it to be fulfilling and rewarding in many ways.
Now, to your sub’s concerns of becoming a doormat. I have no choice but to parrot what others have said. The best way to mitigate her fears in this arena is through your Dominance. The more she experiences your care and attention, the less worried she’ll be of becoming a doormat.
Now, if she fears becoming a doormat to the rest of the world, this is a bit different but, still fairly easily overcome. Many subs are dominant and powerful people in the workforce. Their joy in submission comes from being able to turn that off when they are in their Dom’s presence. If she fears that transition between the two worlds, rituals can help a great deal. My lady and I have a ritual for parting ways before work and one for coming back together after. Each signals the power shift taking place, allowing her to adjust her mindset accordingly.
In either case, the key is your Dominance and leadership. So long as you’re in control and keeping her best interests in mind, things will work out just fine. I wish you and your Mrs the best of luck in your journey.
Regards,
MasterOfAngels