Krishna explains in the Bhagavad-Gita
(9.10): 'Under My superintendence the material energy is working'.Apart from
the material, external energy, there is another energy - the internal
energy. By the internal energy the spiritual world is being manifested. As
the material world is manipulated under the external energy, the spiritual
world is conducted by the internal potency. That internal potency, called
the Hladini Sakti, is Srimati Radharani.
In CC Adi 1.5 it is said The loving affairs of Sri Radha and Krishna
are transcendental manifestations of the Lord's internal pleasure-giving
potency. Although Radha and Krishna are one in Their identity, They
separated Themselves eternally. Srimati Radharani, as the highest
devotee of Sri Krishna, derives the greatest pleasure in serving Him. She is
the origin of all the Gopis and of all the Goddesses of Fortune (Lakshmi
devi) who are engaged in the service of the Lord. She is the mainstay, the
ideal and the ultimate refuge of all devotees embarking on the path of
devotional service. Without first getting the mercy of Srimati Radharani it
is impossible to even approach Sri Krishna.

The Hare Krishna maha-mantra is in fact a prayer to Srimati Radharani. The
word "Hare" is derived from "Hara" which denotes the
internal energy or Hladini Sakti of Krishna. This is none other that Srimati
Radharani. When one is chanting the maha-mantra, one is saying: O
Krishna ! O Radha !! Please engage me in your devotional service.
Krishna is difficult to approach directly, but He is bhakta-vatsala, always
eager to please His devotees. Thus the mood of a devotee is to invoke the
compassion of Srimati Radharani Who then recommends the devotee to Sri
Krishna. Since Krishna is easily pleased by Srimati Radharani, He then
readily accepts the devotee in His service.
Vrindavan Lila
When the Lord descends, He is invariably accompanied by His loving
associates. Five thousand years when Sri Krishna descended in His original
form, as a cowherd boy in Vrindavan, Srimati Radharani accompanied Him in
Her original form. She appeared exactly two weeks after the appearance of
Sri Krishna on the eighth day of the waning moon (ashtami). Srimati
Radharani was found on a lotus flower by Vrashabhanu and his wife Kirtida
near the village of Barsana, a few miles away from Nandagrama. It is said
that Srimati Radharani first opened Her eyes only when Sri Krishna appeared
before Her. Until that time Her eyes were closed.
Understanding the mellows of the relationship between Krishna and Radha is
impossible from the mundane perspective. Understanding madhurya-rasa
(devotion at the platform of intimacy), which is the highest level of
relationship of a devotee with Krishna, is only possible in the most
elevated stages of bhakti where there is not even a tinge of material
contamination. Therefore Svarupa Damodara Gosvami has written: The
loving affairs of Radha and Krishna are not ordinary, material loving
affairs, although they appear like that. Rascals and fools misunderstand
Krishna to be an ordinary man. They do not know Krishna's transcendental
nature. They try to imitate Krishna"s rasa-lila, His dancing with the
Gopis. There is no offense greater than this. Devotees starting on the
path of bhakti must carefully avoid such offenses. They must simply pray to
Srimati Radharani, as their most compassionate Mother, for mercy, for bhakti
and for an opportunity to serve Sri Krishna.
Qualities of Srimati Radharani
As explained in Bhakti-rasamrta-sindhu (Nectar of Devotion), Krishna
possesses sixty-four transcendental qualities. Srimati Radharani has
twenty-five transcendental qualities, but She can control even Krishna by
them. Her transcendental qualities are as follows:

Krishna means "all attractive", since He attracts every one to
Him. But Srimati Radharani attracts even Krishna. Although Krishna says
vedaham samatitani - 'I know everything' - He fails to understand Radharani.
Krishna is acyuta (inconceivable), but for Him Radharani is inconceivable.
Radharani is so great. Krishna thought, 'I am full. I am complete in every
respect, but still I want to understand Radharani.' This question obliged
Krishna to accept the propensities of Radharani to understand Himself. So
five hundred years ago Krishna appeared as Caitanya Mahaprabhu, in the mood
of Srimati Radharani and with Her golden complexion, as His own greatest
devotee. Krishna did this to understand the depth of devotion of Srimati
Radharani.
Mercy of Srimati Radharani
Srimati Radharani is the ideal maha-bhagvat. As the greatest devotee, She
is also the most compassionate. She is unable to bear the suffering of the
souls trapped in the material world. The word aradhaya (prayers)
is derived from Radha and means worshippable.
Similarly the word aparadha (offenses) means against Radha.
When one performs devotional service, one is pleasing Srimati Radharani and
when commits Vaishnava aparadha against Krishna or His devotees, one is
offending Radharani. Srimati Radharani is the guardian, the mentor and the
benefactor of all aspiring devotees. When a soul starts to inquire about
Krishna, Srimati Radharani is most pleased and takes charge of his
devotional advancements. As one makes progress, one continues to invoke the
mercy of Srimati Radharani and when She is pleased, Krishna is automatically
pleased.
All glories to Srimati Radharani !!