I feel that a more accurate translation would be "Why... why won't you take the hint?" but without more context, I'm not confident enough to edit the commentary. わかってくれる is often used when you expect someone to understand your feelings/thoughts even though when you didn't explicitly say so. I think douki-chan is discouraged by douki-kun acting like he's not aware of her feelings towards him.
I feel that a more accurate translation would be "Why... why won't you take the hint?" but without more context, I'm not confident enough to edit the commentary. わかってくれる is often used when you expect someone to understand your feelings/thoughts even though when you didn't explicitly say so.
I had similar doubts when I translated it, but left it as you see, likewise owing to lack of context.
Next comic's up, and we've got the extra context now!
Even though Douki-chan asked him not to roll down the window, Douki-kun forgot, so now he's let all the pollen in. Life is suffering.
Seeing that, I'm inclined to leave it as-is. "Take the hint" would imply that she's been circumspect about whatever she's trying to get him to do, whereas the reveal indicates she's told him directly and he just spaced out about it. I feel my initial choice covers the intentional ambiguity better. (I'm open to discussion if others feel otherwise, of course.)