Dear Jack,
If you point out the wrong things your girlfriend does, then she can point out the wrong things you do. After all, you are both equal. You are not her father, and she is not your mother. Usually, pointing out their mistakes this does not change the other person. It just leads to quarreling because one person has assumed a position of authority over the other. Also because the other has been put on the defensive. People who are defensive feel they should defend themselves. It doesn't lead to anything good.
A better approach is to point out and appreciate the things she does right. If you do this for each other, the good will grow, and the things that are not as good will become less and less.
I have been married almost 50 years now to the same dear man. Neither of us are perfect. Baha'u'llah said that mates should "live as two birds in one nest." This is the vision of how life together should be. He also said "Make your home a haven of rest and peace." Both of these give a mind picture of how life can be. We need to focus on the good things, and not on the negative things so that good will grow. Ben and I have taught ourselves to live this way and I can tell you that it works. I hope you will try it.
Begin to smile and give her praise for the things you like about her, and the things that she does right. Please do this as a scientific experiment. Than write back to us about the reactions and results. Will you please do this for us?
I hope others here will also test this and let us know your results.
Friendly greetings and good wishes, Mary