trip or vacation with friends (FWIW, I don't think guys only trips are great ideas either). While I probably wouldn't/couldn't forbid my wife from taking such a trip, I'd definitely make my opposition to it known.
I might be able to get behind a sisters/moms/daughters trip, but, I don't think I'd be too happy about my wife taking off for days at a time with her girlfriends...especially non-Mormon girlfriends who were likely to be consuming alcohol. Again, I may be old-fashioned, but, married women have no business hanging out in bars. Much less so without their husbands. That's just begging for trouble.
If my wife expressed interest in having a "girls vacation" with her friends, I'd probably be concerned. Gratefully, my wife has never expressed any interest in anything even remotely like that. I think married people need to have their own time and their own space...I send my wife to the spa with her mom and friends several times a year...I don't think anything more than this is a good idea for people who value their marriages.