Under my definitions your situation is not "just right" or "fair" and her treatment of you is even worse...

Generally I avoid using the word fair; however, there is clearly some kind of favoritism going on...and I'm so sorry your mom does this...maybe my tangent will help others realize how their actions can effect their children...parents need to budget...considering your mom was unable to get you anything (a card would have been nice) a just right gift to brother's girlfriend would be a card...