It was 2.5 years for DH & I from meeting to marriage. We met when I was 26 & he was 31.
Really, the length of time someone dates or lives together or does whatever without getting married isn't an issue if both folks in the relationship are truly fine with the arrangement. And there are some folks who feel no need whatsoever to be married, and will be together their whole lives without ever getting married.
The problem with your friends is that they seem to be on 2 different pages with regard to marriage. Based on her reaction at weddings, she wants to be married. Regardless of her reasons...and people get married for many reasons...marriage is a life goal for her. It doesn't seem as if it is a life goal for her boyfriend. In this particular case, 7 years is more than enough time for him to have decided whether or not he wants to marry her. The fact that they are not married or engaged leads me to think he has no interest in marrying her. He may not have an interest in marrying anyone, but he certainly has no interest in marrying her.
I'd break up with him. I wouldn't give him an ultimatum. I wouldn't cry, carry on, and scream about it. I'd say "Marriage is a life goal for me, and it's not for you. I need to find someone whose life goals are similar to mine, so I don't spend my life angry and frustrated". Certainly it won't be easy, but it won't be any easier another 7 years from now, when she's got 14 years invested into the relationship.