"Meaning, we all need to communicate about our feelings. My intuition tells me, this is a chance to get everything on the table and talk about how I'M keeping the family apart."
Let's say you do go to the counseling session. The counselor should make sure there is a common agenda right at the start of the session, such as going around the room and asking the respective members what they understand the purpose of the session to be. If you find the session to be going off topic and unduly focused on you and your mother in law's agenda of cutting you down, blaming you, etc, you are within your rights to leave the session. You might want to discuss this with your husband beforehand. OTOH, I agree with the other posters that you don't necessarily need to go to the session if you feel it won't be productive.