The snapping noise they make?

I just adopted my friend's female betta fish. I have my own female betta fish, and I've had her since February. They both make bubbles, of course. But my friend's fish's bubbles are LOUD. Like, it sounds like a snapping noise. And I KNOW it's not the bubbles popping. Is she snapping her jaws? What does this mean?
She gets breeding stripes whenever she is fed, when she sees red, and when she sees me. But she doesn't have a real bubble nest, just making these snapping noises. The bubbles she makes are big, and they don't pop. And she doesn't usually have breeding stripes when she makes the snapping noise.
2G Cylinder tank, gravel, one large rock, amazon sword, and marimo. Ammonia 1 step worse than "perfect"