Not comparing to the other couples in the show.. also not comparing to sam and arjun too..
but this particular scene showed a different feeling altogether _ according to me arjun is already in love with radhika and it shows.. but his revenge comes first and as for radhika it is not love but the care and dosti towards Sam and at the same time there is a comfort level btw her and Arjun which is not there btw her and Saral.. notice that with the way they talk with each other. Seeing the fact that sam is happy with arjun, radhika shows respect towards Arjun.
And as far as Sam flirting with Arjun, its normal bcos she is in love with him and he is her future fiancee. Nothing to be said cheap just bcos we like Ardhika together.