Y'know . . . just because you were roommates back in the last century
doesn't mean that the two of you have continued to have much in common now that we're well into this century.
It appears pretty obvious to me that your former roommate thinks
(whether consicously or un-) that she chose the wrong brother.
And I think she's angry that you've "caught" this winner
and that she's stuck with (what she perceives as) a loser.
How sad.
I'm guessing some of the other moms here will have some wise advice about how to remove yourself from this woman's nasty remarks . . .
while you are pregnant, you want to take good care of yourself and not expose yourself to negative (nasty) input.
Because you're married to brothers, I imagine you'll have to see
one another at least some of the time at family gatherings.
But, the rest of the time, I think you can find other ways
to fill your time productively.
Wishing you a happy healthy baby and a joyful successful marriage.