Hi OP, I feel very sorry for you.
Basically, it is sexism. It's irrelevant how much your earn - if you were a SAHM she would probably still disinherit you based on what DH earns. The point is that the boys are the "providers" and she wants to make them at least equal to your DH and you are the "carer" who is expected to run around after everyone and provide unpaid labour. It's really up to you how much you want to be seen in this way - your aunt clearly has the same values.
One of the reasons why splitting inheritances equally is fair (aside from the emotional/favouritism aspect) is a form of Rawlsian philosophy in terms of splitting the cake. It's not possible to be precisely fair, because the clock on what you all have doesn't stop when your mum dies - your husband could get ill or leave, a brother could win the lottery or get a better job, or a brother's wife could leave and take him to the cleaners. I think that there's a case for a less equal split if, for example, one sibling's basic needs cannot be met without it, but this is not in that territory and your mum is being very unfair.
When your mum says she has given you a lot of time, is this unencumbered mutually agreeable time, or time where you need to make yourself available to do something for her? I'm not saying there's no value in time, but often people don't really value women's time, or the things they might do for themselves if they were not running around pleasing someone else.
You are allowed to feel sad and disappointed. I think it is healthy to try to get a bit of distance and I think it is helpful to frame it in that way to your brother and aunt - it's her decision and you just don't see her in the same way, so you are distancing yourself to protect yourself from further hurt.