Oh come on - of course we are all very Panhellenic minded and supportive of all groups. But, we have discussed TO DEATH on this site the whole tiers/perceived tiers issue in SEC recruitment. It is a fact. This mom is just verbalizing what she is seeing, and you all know that she is probably telling it accurately.
Yes, let's do all we can to support all groups on campus. That is, in fact, what the OP is saying. These women were extremely supportive of their own houses UNTIL one of their daughters joined another (perceived) more desirable (stronger) house. Now it seems to close friends and pledge sisters that these moms no longer identify with their own houses and (read between the lines!) one of these moms is acting very 'new money/moved from the wrong side of the tracks/acts like her stuff doesn't stink, etc' and it is irritating.
OP - I get it. Just smile and wear your own pin/button proudly.