Maybe a few things... isn't it always?:)
First, is your letdown changed and more quick now that your body's more "experienced"? If so, you could self-express for a minute before latching her and it would be slower to flow.
Second, have you changed your eating habits? Sometimes when you drink less water, or eat less protein and fats the milk changes flavor. If you have changed, perhaps reverse and then gradually change back to your current diet to get her slowly "used" to the new flavor.
Or, finally, where do you nurse? Is it loud or bright or "distracting"? When I first started, I was in a quiet room without bright light and really concentrated on my newborn, but as she got older, I switched because we were both "pros", but she was distracted and paying more attention to the world, so I had to revert, and again, slowly add the "distractions" back to the environment. Then, no trouble. Or, have you changed something simple, like your favorite spot/chair, or added a coverup? Those were also problematic for my child, and I had to revert to what she was used to for her to revert her behavior.
Be proud of yourself for working through and continuing to nurse -- sometimes you get bumps in the road, but the bonding is so worth it and so rewarding for you! Good luck:)