As we can not see our breaths but a living body is a testimony to their presence, similarly we may not directly find much reference to Shri Radha in our scriptures but Her presence is obvious all around because no mention about Lord Krishna is viable without Her. Shri Radha though indistinguishable from Lord, holds our finger and takes us to Him just like the invisible fragrance enables us to locate a flower. Also, love contains an unquenchable thirst, represented by Shri Radha while Sh Krishna represents fulfillment. So Radha- Krishna collectively symbolizes the divinity of love, wherein there is no point of saturation despite the perpetual proximity. This is referred to as Maadnakhya Mahabhaav. (Read Pad-Ratnakar 292, 293, 296, 297 for further clarification).