I would set up a face-to-face conference with her. Sometimes, things can get misconstrued through email. This will give you a chance to talk to her about your concerns and she can talk to you about hers. Hopefully after this conference, she will see that you are fully capable of doing your job.

It seems that all your efforts are reactive, I would strongly recommend a proactive approach. First of, I would reach out to the parent with a positive communication about her child's performance in class. It does not have to do with the student's academic performance, it can be about his participation in class assignments, collaboration with his peers and helping out in the class. We call these sunshine notes and the parent responds well to these as they feel that their child is being appreciated for their contribution in class. Once a positive rapport is established with the parent, they can be invited for a meeting where you can plan the course of action for future assessments and feedback. The teacher can offer to send the study guide home or email it to the parent before the test.

In addition to solutions already posted, I would probably state your expectations for parental emails in regards to grades, grading, etc. In the same manner that there are procedures for phone calls and conferences, the parents should know that by the 10th grade, grading concerns could first come through the child ( as you told the students to see you after classes for concerns), and that the grading procedures are outlined in the rubrics. If there are any concerns outside of what is explained, then email. Otherwise I would give the explanation that is on the rubric. If the parent just wants to dominate, I would document everything and have administration get involved if necessary.

It seems like the parent is creating an excuse for her child instead of making him accountable foe his work and education. I would post the rubric for each major assignment on your teacher website. Have students to get the a signature that parents have read and understood the expectations of the assignments.

I would suggest a parent-teacher conference with the student present so that you all can discuss that grades, and how she can trust your grading and see all your feedback without having to contact you constantly.

Advise her politely that the rubrics are there for a reason so her questions will be answered. Also advise her that her son never asks her questions.

Set up a parent teacher conference. Explain the rubrics in person. Given them the break down in points. If it is an email, it is easy enough to just reply to the email with "Please see rubric for this assignment. Thank you." Eventually they will get the point. Or just bear with the parent and answer the questions he or she brings to you. You can't force a parent to trust you. Trust is earned, not given. It'll just take time. Or it won't happen and you'll just have to deal with the parent.

When giving an assignment, I would be sure to also email her a a copy of all rubrics, checklist and other materials that will be used to grade the assignment and ask her if she or her child has questions beforehand. This way, you are being proactive with your communication without having your grading criticized.