From everything you have said, this woman is a BULLY and feeds on it. You have described a pattern of behavior. I assume this is based in a academic envirnoment. It could differ if it is a private vs. public school system... However, this is NOT good. This woman seems like a destructive force.

Do you have a school guidance counsler that could act as an advocate? ...or is that her husband that is your mentor? Either way, she is UNPROFESSIONAL and what she is doing is ILLEGAL. While I have not encountered this in a sports activity, I have come across teachers who are self-rightous in their bullying and sense of authority.

YOU don't actually have to confront her if you don't want to. There is a proper channel/process to handle these type of situations. File a complaint. You cannot be the first person to have issues with this woman, but you may have to be the first person to go on official record. If her husband is part of the problem... he needs to be held accountable as well.

Institutional discrimination (it falls under your constitutional rights, Civil Rights Act, Title 7). It is real. By you being the student, and these people being in a position of authority, you are being targeted and left with little to no power. Take it back. Give yourself a voice... even if it is being said outloud by someone else (i.e. guidance counselor, principal, etc.). Discretely, ask around... would anyone else consider adding their complaints to yours (or even sign a petition). You are not alone. She feeds on making you feel isolated. She had her granddaughter send you that message, because LEGALLY she can be held responsible and the child can't.

God, I am so outraged for you. I'm sorry if I'm not helping, but I just thought you should know all of your options.