True, it is a big part of the story, but we need to see how her arc in Episode 8 plays out to know how much importance is placed on a weapon. Perhaps she is embracing the Dark Side in her fight with Kylo Ren, so she’s going down an Anakin Skywalker path. In this case the importance of the lightsaber in this scene is justified.
Well, that’s an interesting way to look at it, and I’d be curious to see if they explore that at all. But I tend to believe the importance that is placed on it (in the film in general and that scene specifically) has more to do with what it means for Rey (the call to the Force) and less to do with its history (and dark side usage).
Apologies for pulling us off topic a bit.