Oh OP, I do feel for you. Having a difficult relationship with a parent carries so many emotions, often the biggest being guilt. Until I went no contact with my dad, I would assume that our difficult relationship was due to my failings and it's only since becoming older and wiser, that I realise these are his failings not mine. You've already said the truest thing - would you ever treat your children the same way? No. That tells you everything you need to know.
So, for now, you have a couple of options about what you do right now, as her being in your house, making you feel terrible isn't sustainable. The biggie is that you ask her to leave, but I totally understand why that will feel hug and you may feel it's not doable. Firstly, do you think you could say that it feels a little claustrophobic and could she hire an AirBnb for the last month? If this is a big no, which I understand, are there any family or friends she could visit or stay with to give you some respite? If she's the one saying she doesn't feel welcome - use that as a reason for her to leave, as she can barely argue with the things she's said herself. Except, of course, I know she will...
If her cutting her stay short isn't possible, what can you do to protect yourself and your time so you're away from her? Are you out at work during the day? Are there particular times she tends to be around the most? If so, how can you be elsewhere and away from her nasty words? Can you, DH and your lovely kids be busy in the evenings and weekends? Meals out? A trip to the cinema (especially on two for one nights!)? Visit friends? Swimming? Do your kids do activities that you can stay out at, and grab food afterwards? Even an evening walk to the park with a bag of chips will get you out of the house. Can you pick a city and visit each weekend so you're out of her way? I fully appreciate you shouldn't have to, but at least you won't be a sitting duck waiting for her next jibe or sly comment.
Well done to your lovely husband for seeing exactly what she's up to and holding her to account. If all else fails, just keep doing the same, again and again and again, and she may tire of it. Please know you're not alone, and that you don't deserve this. Sending love x