There will probably be a fight even if there isn't a misunderstanding. In fact I think that's more likely. Hayoung has been keeping secrets, which is fair enough, but she's lying outright now, about things that are kind of important. SeoWoo wants to move forward with her and take the next step, but she can't do that if Hayoung doesn't trust her.
I agree, esp the foreshadowing from before (with Hayoung saying how she & Seowoo haven't fought yet), I feel a fight coming on soon.. 0; Hayoung did lie and caused Seowoo to worry, which could've been avoided if Hayoung just told the truth.
,,,,she'll misunderstand that scene uhhhhhg can't wait for her reaction (fighting)