(Also, Slaanesh is more than sex, just like Tzeentch is more than 'god-oh warp magic'. Excess in all forms. Even that ONE GUY who tries WAY TOO HARD to be perfect in whatever he does [anything really]...he worships Slaanesh too)
um.... Is it just me, or does she look like shes drunk and\or high, or now that I think about it, possibly very tired is an option. Also wow, now I can really see those teeth to holy crap I mean in none of the previous images of her did her teeth look that big but at least now I can see just how messed up they are, poor lass. P.S. by not shoes I assume you mean either boots or scraps made to resemble such things.
Have you ever been to a gig with a group of friends that was fun at first but in the end starts to drag - you really want to head home, but you can't because everyone else wants to stay out and you feel stuck and don't want to slink off like a no-mates? That bitter-ender is Cultist in Slaanesh form, still raving and jumping around to increasingly dreary music when all the others just want to go to sleep, but still have to shuffle along behind her because they don't want to appear "boring".
Well, she gets points for trying. Also personally I think Slaanesh gets off on annoyance, so that might be her form of worship. Honestly it seems that's what it boils down to for the worship of every single chaos god with her. Annoy people to piss the off for Khorne. Annoy people for Slaanesh's pleasure. Annoy people to further Tzeentch's plans? Seems like a long shot. More likely Tzeentch enjoys being a troll and sending her to people for no reason. Annoy people literally to death for Nurgle maybe? Or maybe just rot their teeth with candy and waffles. either way.