Invited to bachelorette party but not the wedding...

I got invited to a bachelorette party for a girl that I know through my FH. Him and her FH had been friends since middle school. Her and I are more on the acquaintance side, unless the boys are involved we don't associate. However her MOH is throwing her a bachelorette party which is going to come with a somewhat hefty price tag (which isn't an issue but at the same time it kind of is after trying to recover from the holidays.) As of right now we are not invited to the wedding which is happening at the end of February last we had heard from other friends. Personally I'm not all that interested in what they have planned and also feel rather uncomfortable with the whole thing since we aren't really friends to begin with. I know etiquette is if you're not invited to the wedding you're not invited to the parties. I don't really know how I got included in it all I've tried figuring it out and asking but never got a straight answer from anyone. Just looking for some advice on how others would handle this.