Dealing with a narcissistic MIL

My husband's mother is awful for lack of better words. She extremely manipulative and abusive and lost custody of my husband and his brothers several times until she officially signed her rights over when my husband was 16 and left him in foster care. Before that she used to lie and say he was a self harmer. That he was wanted to hurt the family. Anything to get him locked away in a mental hospital. She at one point planted drugs on him to try and get him arrested but he found them in his backpack before he left home and took them out. The police showed up to his school and checked him. She abandoned him and his brothers in a trailer for a man who beat on them and his father would SA them. In foster care my husband was separated from his brothers and experienced more abuse and his mom didn't care.

He's tried to rebuild the relationship over the years. All he's ever wanted was to be loved by his mom but she goes out of her way to ruin everything. His recently had a birthday and turned 30. We celebrated and his mom gave an awful birthday toast about my husband's sexuality. My husband is bisexual. He only ever dated one man before me and the whole thing turned out abusive and his mom made this awful speech about how he can't claim he was SA'd as a child anymore because clearly he liked it enough to turn out gay. When he's not gay he's bi.

She's awful. I think my husband is truly opening his eyes this year. Last year he made a stupid decision without asking me and came to regret it. His mom begged him to cosign her lease. She said she knows she made mistakes and she wants to be better. All this b.s. My husband cosigned and she maybe pay rent for 3 months and then started missing payments so my husband had to pay double rent to keep from it hurting his credit. She has stopped paying rent all together AND got back with that boyfriend she abandoned my husband and his brothers for and moved him in. My husband and I decided he's not cosigning a new lease with her because her lease is up end of this month. Her credit is so bad that if she can't find a cosigner her apartments won't renew her lease. My husband made it clear he wasn't renewing it and they started arguing. He finally told her all his feelings about everything she does to him and how she hurt him in the past. This was her reply

How do you even reply to something this disgusting?