In law situation

So my mother invited my husband and I and my son to dinner for my little brother's birthday. I haven't seen them in awhile and they really want to see our son, the thing is we don't have enough money right now to pay for both of us because our money is tight right now .. my mother told me her husband will pay for me but not my husband 😔 and the way she said it was kind of rude which I feel disrespected because she said that I could bring him a doggie bag back like wth..Furthermore it's my little brother's birthday and he has never seen our son ... What should I do ? 😔😔 BTW my husband has no problem of me and my son Just going I just feel upset about it ..