Hi brides/brides-to-be/community members

My wonderful fiance proposed to me back in May of this year, and we decided on a wedding date of February 20th 2016! It's coming up fast, and I have spent the last 3 months planning meticulously to make sure we are on track to have the best wedding possible. My parents, being traditional, offered to pay for our wedding, which has been absolutely wonderful. However, I'm starting to go down a slippery slope of stress and anxiety during a time that should be one of the happiest times of my life.
To provide you the cliff notes to my already existing saga, my brother proposed to his fiancee last October. Her mom is alive and well, but cannot afford to help her daughter pay for anything, so she doesn't feel comfortable being involved in the planning process. They also have decided on a destination wedding (3+ hours away from their home), but cannot afford to make the drive even just once every few months to meet with vendors. They are getting married in the same city I am getting married in (which I also live in) one month after I get married. Enter my mom. My mom has explained to me that she now has to be my future sister-in-law's mom, otherwise their wedding would never happen because my brother and S-I-L are completely unorganized. On top of my mom attending wedding extravaganzas, meeting with the photographer, baker, and the venue in their place, they have requested she drive four hours to their home with cake samples for them to try to make sure it's to their standards.
I recently went wedding dress shopping (and found one! :-D ) and my mom spent half of the day texting my future S-I-L because she was having a meltdown of some sort. Her meltdowns happen often because she was the 5th child of 5, and creates a scene to ensure she's important and loved. Those are my mom's words, not mine. My mom explained to me she had to text her all day because 'she needs to find them a DJ for their wedding.' My mom has also canceled on our cake tasting because she has to do something else for them even though I planned months in advance to make sure she was open. She constantly compliments me on my organization during the planning process, and compares my abundant skills to the lack of skills of my brother and S-I-L.
She is planning so much for them because she's now her mom. She has completely forgotten that she has one biological daughter, who is only going to go through this wonderful process once. I feel so pushed aside, and to be perfectly honest, I'm completely disheveled right now. My mom and I had an okay relationship growing up, and our relationship has really blossomed since I've left the house and become an adult of my own.
I am aware that I need to talk to her, however, my mom is an expert of holding things over others' heads. This is why our relationship wasn't a strong when I was living under their roof. In other words, she can be very passive aggressive and knows how to give a strong cold shoulder. So, I'm lost. I really miss my mom. I feel cheated from a huge moment in my life that I always dreamed of experiencing with her.
Do I talk to her and risk her rearranging some plans for her to be a little more available to me, but know that she'll be emotionally unavailable to me because she won't like that I'm calling her out, per say? Or, do I keep moving forward and lean on other lines of support (i.e. MOH, groom's mom, bridesmaids, friends)? Am I acting selfishly that I want more time with my mom even though I'm completely capable of planning and executing that perfect wedding without her input?