@Yunyo - Her expressions tell you what she's thinking.
The first time you can tell she's a little conflicted, feeling strange, and you see her thinking deeper on it afterwards.
The second time she is smiling and meeting his gaze directly. Then they dance together.
She's saying those words, but what she's feeling is that the meaning behind them has changed. If I had to put words to it. The first time it was conflicted. The second time it felt wrong that she was enjoying it. Basically, she's coming to care for him as a companion.
Ok after seeing this chapter I guarantee you all this fandom will turn from SoL enjoying paradise into that one that always complain that there is no progress made romance-wise as if it was the point of the manga.