Priya has been in love before (remember her confession about Ashwin to her Dad?), so the feelings and attraction that feels towards Ram is not new. Perhaps it's been more than a few years since she last experienced it, but it is definitely familiar. Therefore, she has admitted to herself, her Dad, Krishuji, Apeksha and to Neha that she is in love with Ram. She knows it and is enjoying the moments. And she's not entirely immature about it, or else she would not have been so direct with everyone. Ram on the other hand, is blissfully unaware of these sorts of things, and these feelings and physical attraction toward Priya is COMPLETELY new to him, therefore he is taking slightly more time than Priya to recognise and acknowledge it, he just wants to make sure that what he is experiencing is indeed love and not just a deep sense of caring for a friend. I don't think that they are immature, they just have different ways of expressing what they are feeling!!