Here's my suggestion:
However many women are attending, have everyone make that many cookies for everyone. "Their" bag would be shared at the party, the rest distributed to everyone else so everyone walks in with the same number of cookies that they walk out with (minus the shared cookies).
Example: Have 16 people make 16 bags with 16 cookies each. Then one bag of each cookie gets opened for the tasting, and everyone walks away with 15 bags of 16 cookies each, that they did not bring.
To make less cookies: You have 15 guests, so that makes 16 women total attending. Everyone makes 112 cookies (16 bags with 6 cookies to distribute to everyone, plus 16 cookies for all to taste).
Want to make even less? Fine: Have everyone bring 16 so everyone gets to try one, then 32 more so everyone leaves with two of each cookie. Make 48 cookies total, or 4 dozen.
As guests arrive, take ALL the cookies to the kitchen and have one bag opened and set out (on a tray? in seperate bowls?) and numbered for the tasting, then seperate the rest of the bags to be distributed into sacks with guest names on them, so they all have the same thing and number of cookies to take with them. Once everyone has arrived, you can have a tasting and award a prize for prettiest cookie, best tasting, best presentation, or whatever.
My mom's sorority used to do a candy exchange for years! She would bring home peanut butter balls, fudge, peanut brittle, homemade caramels, 'strawberry' candies, peanut butter fudge, etc. It was fantastic!