Oh I had the same issue,but mine was gates. Oh dear was it an issue. The trainer at puppy school taught us to walk up to the gate or door in your case, on lead and make her sit, feed her a treat and pat her. We then would hold a tight lead and slowly walk her through the gate saying " good girl" and then on the other side we would treat again and give her lots of pats and "good girls" we did this at least three times a day for 3 weeks but she gt there. hope that helps. )
The other bonus from this is she always waits at doors now, it's great!