having problems with holding the center line on the runway
First off, I never have trouble with the centerline staying on the runway, where I fly it never moves, it is painted on just fine.
Second, get a new instructor, women shouldn't fly and we certainly know they spend enough time telling us what to to the rest of our lives.
Third, if you absolutely have to fly with her, next time yell out "back off biatch, I'm in the left seat and I'am flying this aircraft".
heheheh If you follow number 3, you will probably have a new Instructor shortly, possible at a differant flight school.

You have been given some good advice, relax, stay on the pedals, look down the runway some, it will be handy if you can get the hang of maintaining centerline as alot of examiners will watch for that on your checkride.
dago