recruitment

Some do. Some don't. Depends on whether that matters to you which one you end up in.

agreed some do some don't but I can say I didn't buy any new clothes and I have no idea what brand they were and ended up in a "top tier sorority"... I wouldn't worry about this as much

In most sororities, the members aren’t technically allowed to make any direct comments about a PNM’s appearance during voting. I’ve noticed girls in my chapter will try to get around this by saying something like “she’s really trendy!” or “I can tell she’s really unique and into fashion!” which is basically code for like “She was dressed really nicely/looked pretty”. Honestly I think it varies more so on an individual basis of each member. Some girls I know seem like they’re actively paying attention to how the girls dress but others don’t seem to notice.

Some chapters will care more about that kind of stuff than others. I wouldn’t stress about brands regardless, I think just simple outfits that look polished and flattering will be fine for even the chapters that are more superficial.