I just graduated from WKU so I can give you some insight to what OPAGal can experience.
Alpha Gamma Delta and Sigma Kappa are participating in active COBS (actually AGD is having a huge one soon!). The Greek Life office at WKU is not really all that helpful too be honest because they employee greeks who are favorites of the advisor.
That being said, no you don't have to go to mixers or even dances if you don't want to. There are mandatory events, but they are usually all greek events, rush events, etc. Nothing like parties or anything. Sisterhood retreats are a lot of times, but those are things you want to be involved in!!! At AGD I know we have sisters that are in other service sororities and also Delta Omicron. We try to have a diverse group of women. I am sure the same is true for Sigma Kappa.
If you are interested in informal recruitment, let me know. I can give you contact names for both AGD and Sigma Kappa. Although I know I am partial
you should definitely figure out where your home is. There are wonderful points to each sisterhood at WKU. And I know you don't want to miss out!
Sarah