@throughstars
My interpretation of it was that the "medicine" was her continuing to pretend she wasn't in love with him and that she's fine with just being friends with benefits. When she "stops taking the medicine" she's admitting to herself that she's in love. And when at the end she says she'll "cure herself with willpower" she'll try to get over him.
@kanozo Thank you for this information, it did clarify for her side.
However, I'm still confused with the guys side. He said he was planning for shotgun marriage. Does this mean his planning to pregnant her? Or was it for someone else?
@throughstars
I don't think he was planning on getting her pregnant I think he just meant something along the lines of "if I slept with a woman and got her pregnant by accident I would marry her out of obligation, that's the only way I would ever get married". Which saddened her because it made it even more clear he didn't want something serious with her.