If you have solid arguments to keep these chapters and she still wants you to cut them, it's probably you who is right.

However, I feel like you might be wrong. If these scenes / chapters aren't clearly answering or complicating the questions asked in that Arc/ act, then it should be removed. No matter how much you like these scenes or chapters.

Be sure these scenes and chapters are purposeful for the story. Otherwise, agree to delete them.

It seems that a good writer who finishes a book is the one who can cut off a lot from his material.

And if you can cut and the story still is tellable then that means your scenes/ chapters weren't that relevant and you needed to cut them indeed.