In this way, without Radharani there is no meaning to Krishna and without Krishna there is no meaning to Radharani. Because of this, one always pay respects first to the Lord's internal energy in the form of Radharani, and then to the Lord. She is the mediator without whom access to Krishna is not possible. Thus They are referred to as Radha-Krishna. In this way, Radha and Krishna are one, but when Lord Krishna wants to enjoy, He manifests Himself as Radharani. Otherwise, there is no energy in which Krishna can attain pleasure outside Himself.
SRIMATI RADHARANI ASHTOTHRARA NAMAVALI
Gandharvika, she who is expert in singing and dancing
The only girl desired by the prince of Vraja,
4] Gandharva radhika
Who is worshipped by the Gandharva-angels,
Whose luster is like the moon,
Who accompanies Madhava.