No, you can ride in our lane, MC. I know that the philanthropy had zero to do with the sorority I joined. I think if, say, you had someone near you go through breast cancer it can maybe make you look twice at ZTA if you hadn't before, but when it comes down to it I would say maybe 0.00001% of girls join because of the group's philanthropy.
As for deludanoid mom:
1) Show her some of the "my perfect daughter got cut" stories on here. Tell her she is setting her daughter up to fail, period. Not only that, what if she hates mom's sorority and they hate her? Even if she gets in or Mom buffaloes her in, no one will be happy. Then again I don't think that sort of parent really cares about their child's happiness, they care about them being the perfect ornament to show their "accomplishment" of child rearing.*
2) "I would love it if you pledged the same group I did, because I've gotten so much happiness and so many lifelong friends from it. However, I know that campuses are different/chapters change over time and I want you to join the group that will make you the most content. So don't get too focused on XYZ."
Also: if Mom has a Facebook page and is reconnecting with her college friends, it can help to show Daughter how many of those friends were from different sororities and not just her own. In other words, this is not just lip service about other chapters being awesome.
*Does it bug the living f%&k out of anyone else when you hear a parent say "my greatest accomplishments/achievements are my children"? Getting the deck refinished is an accomplishment. A child is a living breathing human being.