The girl from the rich family writes to the guy who she has now developed feelings for:
I've seen 応えたい with words like 期待、要求 or 想い, but with 日々? Does she implicitly mean "the happiness I have felt during the days I have spent with you"? And that she wants to give the same happiness to him? Or is it more along the lines of "I came to think that I want to make the time we spend together a happy one"?