Robyn will develop the habit of trying to sneak up on other people when they talk to someone and let rose petals rain down on them (throw them at them). She'll also start to carry a small bow and tiny arrows with herself - basically styling herself as Cupid trying to set up everyone with everyone. As this is only a habit, not a conscious attempt to set up people, she'll only notice what she is doing at first, without an explanation to it and without a reason for her actions that she could give. She'll just find herself doing them (You are free to expand on this, like having her carry around romantic violin music or something similar.)

If this does not work and you'd rather have something else, please say so.