Sorr to cut and paste but have you read 'Toxic Parents' by Susan Forward? Extract as follows - you will see your mother's behaviour here;
"Once you get going, most toxic parents will counterattack. After all, if they had the capacity to listen, to hear, to be reasonable, to respect you feelings, and to promote your independence, they wouldn't be toxic parents. They will probably perceive your words as treacherous personal assaults. They will tend to fall back on the same tactics and defenses that they have always used, only more so.
Remember, the important thing is not their reaction but your response. If you can stand fast in the face of your parents' fury, accusations, threats and guilt-peddling, you will experience your finest hour.
Here are some typical parental reactions to confrontation:
"It never happened". Parents who have used denial to avoid their own feelings of inadequacy or anxiety will undoubtedly us it during confrontation to promote their version of reality. They'll insist that your allegations never happened, or that you're exaggerating. They won't remember, or they will accuse you of lying.
YOUR RESPONSE: Just because you don't remember, doesn't mean it didn't happen".
"It was your fault." Toxic parents are almost never willing to accept responsibility for their destructive behavior. Instead, they will blame you. They will say that you were bad, or that you were difficult. They will claim that they did the best that they could but that you always created problems for them. They will say that you drove them crazy. They will offer as proof the fact that everybody in the family knew what a problem you were. They will offer up a laundry list of your alleged offenses against them.
YOUR RESPONSE: "You can keep trying to make this my fault, but I'm not going to accept the responsibility for what you did to me when I was a child".
"I said I was sorry what more do you want?" Some parents may acknowledge a few of the things that you say but be unwilling to do anything about it.
YOUR RESPONSE: "I appreciate your apology, but that is just a beginning. If you're truly sorry, you'll work through this with me to make a better relationship."
"We did the best we could." Some parents will remind you of how tough they had it while you were growing up and how hard they struggled. They will say such things as "You'll never understand what I was going through," or "I did the best I could". This particular style of response will often stir up a lot of sympathy and compassion for your parents. This is understandable, but it makes it difficult for you to remain focused on what you need to say in your confrontation. The temptation is for you once again to put their needs ahead of your own. It is important that you be able to acknowledge their difficulties without invalidating your own.
YOUR RESPONSE: "I understand that you had a hard time, and I'm sure that you didn't hurt me on purpose, but I need you to understand that the way you dealt with your problems really did hurt me"
"Look what we did for you." Many parents will attempt to counter your assertions by recalling the wonderful times you had as a child and the loving moments you and they shared. By focusing on the good things, they can avoid looking at the darker side of their behavior. Parents will typically remind you of gifts they gave you, places they took you, sacrifices they made for you, and thoughtful things they did. They will say things like, "this is the thanks we get," or "nothing was ever enough for you."
YOUR RESPONSE: I appreciate those things very much, but they didn't make up for ....
"How can you do this to me?" Some parents act like martyrs. They'll collapse into tears, wring their hands, and express shock and disbelief at your "cruelty". They will act as if your confrontation has victimized them. They will accuse you of hurting them, or disappointing them. They will complain that they don't need this, they have enough problems. They will tell you that they are not strong enough or healthy enough to take this, that the heartache will kill them. Some of their sadness will, of course, be genuine. It is sad for parents to face their own shortcomings, to realize that they have caused their children significant pain. But their sadness can also be manipulative and controlling. It is their way of using guilt to try to make you back down from the confrontation.
YOUR RESPONSE: I'm sorry you're upset. I'm sorry you're hurt. But I'm not willing to give up on this. I've been hurting for a long time, too."
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Have a look at the Stately Homes threads in relationships - there are a lot of us there with similar issues.