Lainey, teaching, and med school...
I just watched the movie again and on a second viewing there were things that bothered me about how the script dealt with Lainey wanting to get into med school.
Because first, why does she want to get into med school? We don't know, it's never shown. On the other hand, in the film we learn about how much she loves teaching kids and there are even two scenes dedicated to how good she seems to be at it. It appears that the only reason Lainey wants to go to med school is because the writer of the script needed to set up an obstacle between her and Jake (see: Lainey moving to Michigan).
The second thing that bothers me is how she more than once gets taunted for being a kindergarten teacher. First by her Adam Brody boyfriend who says something like "teaching is not a real thing", and later by Adam Scott's character who seems to want to hurt her by asking what she does for a living right after he and two other characters have proclaimed more "high status" jobs for themselves. After that line from him, Lainey starts crying and goes to the bathroom. In one of the film's later scenes, Scott's character says to Lainey: "just because I don't applaud your intellect doesn't mean I don't notice it", which makes me think Lainey, who we know has low self worth, has been chasing his approval (and considering that other scene with her, it appears that to get his approval she would have needed a different education and a different job).
With all of these scenes in mind it feels a little bit like she's going to med school to prove her intelligence to other people, which is probably not a great way to live one's life. I imagine this interpretation was probably not the writer's intention but I believe it's still there. It did cross my mind that maybe the writer herself has less high opinions about kindergarten teachers and takes it for granted that no one would rather be that than a doctor (which I'm sure isn't true) and that maybe that's what's coming through in the script.
To sum it up;
it probably should've been made more clear why she wanted to go to med school, because now the only reasons she wants to go is because the film's writing is either lazy or judgmental.