Let the couselor help to determine if a seperation would help or if your marriage really is over. I think you have too much at stake to base a drastic move such as divorce on the advice of a friend. You didn't get medical help for your depression from a friend why risk your mental health in this way. Get a professional opinion. As for the mental abuse, take a good look at it.
Mental abuse can be a very vague term at times.
Sometimes, it is cut and dry and other times it is opinion. A man wants his wife to stay at home after having children. If she doesn't want to but feels pressured to do so, she could call that mental abuse. I do not need the details but please seek help for your marriage. It is the single most important vow that you are likely to make.