I know how hurtful it can be, how invasive, and I also know how difficult it is to ignore, BUT there is nothing you can do. Putting your husband in the middle won’t work, because, I guarantee, that he has spent a lifetime “ignoring” his mom when necessary and he will tell you to do the same.
The reason why this feels so terrible is that you probably do not have an invasive relationship with your own mother and this is so foreign to you. Truly, keep remembering, she means well, ignore her and just keep saying thank you for caring.