Changing-growing-joining the herd?

In any relationship, be it with family, friends or your significant other; some kind of compromise is always required. Putting up with parents, cutting your friends some slack or trying to plase and get along better with your boyfriend or girlfriend. So where are the lines between growing as a person, being amiable, allowing someone to change you for the better or just plain giving up too much of who you really are just for them?
When it recently became apparent how much of a goody-two-shoes a friend's man really is, I think I felt enough outrage for both my friend and I combined. It wasn't so much that he was a goody-two-shoes himself but more that he seemed to be forcing one of my partners in crime into becoming a super holy goody-two-shoes, too, without seeming to consider that he should probably be the one who needs to loosen up a wee bit. I mean seriously, I know I sound a bit idealistic when I say this but come on, not every single bit of physical contact/excitement/show of affection is a slippery slope to erm...morally questionable acts. The other thing that worried me was that my friend seemed all too happy to be someone far more repressed than she really is just to conform with what Mr. GTS wants. It worried me that she seems to be becoming one of those people who make the whole world seem perfect and have picture perfect families (we all know how that usually turns out on tv) and one day I might not even hear of her troubles, regardless of how minute, let alone be there to help her anymore. Now that is a slippery slope that scares me.
But the more I thought about it, the more I wondered. Was I, in fact, the one holding her back from growing as a person? So what if she wanted to shed a bit of her wilder side? But then again, I still very much felt a little alarmed by how easy it seemed for her to morph into what Mr. GTS felt was more appropriate. Is it too simplistic to think that well, if you find someone inappropriate, then they're not the appropriate one for you?
I still can't figure it out. Am I being the concerned friend or am I being the one who isn't allowing her friend to grow? I'm still trying to keep an open mind about it and see it both ways. And the scariest bit is what if this is exactly what happens everytime my man and I get into a huge fight when he's 'done wrong' according to me or when he diplomatically tells me that something I do bothers him?