Although it may not be totally comfortable....I think that older women should be welcome as potential pledges. I pledged when I was 19 (I was a junior in college) and now...at age 28, I'm on my sorority's National Board. After not really being involved for 7 years, I'm surprised at how much I enjoy the group; and also how much I still have in common with the brand new sister's who are 10 years my junior! I mean, I can have more meaningful conversations with them than I can my co-workers that are the same age as me; probably (no definitely) because we share the bond of sisterhood.
Sisterhood is lifelong; you never get too old for it!