Lyric discussion by RyanEatBrain 

I disagree slightly with the other posts.

I think the narrator is friends with this girl who he knows isn't in love with her boyfriend of five years. The whole time she's been with this guy, all her friends have been "staying on their side," not saying anything even though they know she's not fulfilled.

The narrator is trying to get her to think twice about her long term plans for the relationship, since he sees that she isn't really in love. He's saying she shouldn't blindly follow the path she's on.

Referring to her future plans with her boyfriend, like marriage.

The narrator knows she's not afraid of being single or lonely because the narrator has been close to her for five years and thinks he knows her well (or maybe because she's been cheating on her boyfriend with him that whole time and doesn't seem to value her relationship for that reason).

I think he means she shouldn't just go through the motions because her boyfriend says he loves her, as evinced by:

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