Protect her. Respect her. Argue not with her. You can't win and get this guilty feeling.
Open the door for her. And of course, love her. Adapt to her emotional side motivating her.
See in her love and qualities that you see in your mother. Even if they disagree. Realize she is your Queen, now and forevermore. Just stay our of their personal wars.
Hug her. Enjoy her. Even tease her. As long as you're together you'll be discovering her. This will never end. You eventually will be surprised by her.
Not all Queens wear crowns. But you can keep yours happy and it shows in her smile.