That is my main issue with how there are so many hints from Serena, but after the beginning of XY, she doesn't make that much of an effort to try to get Ash to notice her feelings, though that can be understandable of her either trying to understand her own feelings (doubtful since she seems, especially after XY 31, to be perfectly aware of her feelings) or just trying to get comfortable around Ash. I hope that she actually takes steps to get closer to Ash and hint towards him that she likes him instead of these little things we can only see.
I think the problem for Serena not to make that much effort is because Satoshi is still quite oblivious. And she may risk the relationship if she make it explicit. But this problem will be solved if Satoshi being less oblivious if possible later in the series.