In amount of chapters it might feel rushed, but in universe it has been some time since all of this started for them (at least a week or so).
Having said that, I don't even think her 180 and kissing him at the time was all that rushed either. She heard words she probably never imagined she would hear from him: that he loves her. That her love for him is reciprocated. Of course she would flip from being angry to happy on a dime. Everything she had been feeling and noticing about him was untrue AND he loves her. I feel like anyone would be happy about that. Add to it that he admitted he was jealous of everyone watching her and of that probably sent her even above cloud 9.
Holy shit I did NOT expect this and I certainly didn’t expect her reaction lmao. I thought she would be all flustered and this would have been the reaction in her inner dialogue but for her to jump him? Jeez
I hope next chapter we get a continuation on the end here as well as Marin's inner thoughts while she was listening to him. It would be great to see what she was thinking.