This is a good point.
When my SO asks for advice, I'm always more than ready to give it, whether it is about makeup or clothing and I do the same for GG girlfriends (a girlfriend was once determining what clothes she should bring to Goodwill, was this too tight, was that too short, etc). At various times I've also asked my SO or my GG friends if they thought a particular color suited me or was this outfit hopelessly out of style, or was my eyes shadow applied evenly on both eyes. These are specific questions and they don't take all that long to answer. And there is a goal in mind.
If my SO ever wanted me to give her a complete makeover, however, frankly I wouldn't know how to go about it. Over time I've figured out what works for me, but I have no idea what works for someone else in terms of makeup. I'd have no idea how to makeover a GG friend either. :p
But, the idea of spending a "fun" evening with another GG putting on different clothes, trying on different makeup, doing each other's nails, etc, just for the fun of it is another matter. The process is not an activity that most GGs past the teenage years engage in with other GGs, just for its own sake.
Do you see the difference?