why do you feel like you HAVE to square up with her anyway?
For a very practical reason! Whenever I want to say something back to her I have to turn my head. Sometimes she is even slightly behind me, like the woman in my avatar, only closer to me. I just get tired of turning my head all the time, it is a very awkward stance to be in. So I automatically turn towards her.
Do you feel like you need to exert your dominance?
No. Actually I don't try to do anything at all. I just try to have a normal conversation. I certainly don't try to be "alpha" or dominant. I don't look very intimidating anyway. Trying to be dominant is kinda unnatural for me and whenever I tried it, it backfired. These days I am just being ME.
They are giving you their unbridled attention.
Yes, that is kind of what it feels like.