Eh, I see it as yet another attempt to keep the MC at arm's length. Just Quinn things, nothing new.
In fact, every LI on Others path has some kind of an obstaclte MC is supposed to overcome. With Lily it's the whole 'Don't fall in love with me' thing; with Nicole it's the uncertainty that comes with dating a single mom 10 years your senior; with Riona it's the fact that her very life seems to be at stake now not really, but you get it, I think; with Zoey it's her habit of running away from her problems and ignoring her feelings. And with Quinn - it's the thing you mentioned. 'I'll leave your ass, everything changes, deal with it'. Mind you, I do agree with her overall sentiment, but who says some people can't stay in your life for good, especially if you want them to stay, if you fight for it? I believe Sage says something similar in this episode
And it's up to the MC to find solutions to all those problems.