Śrī Rādhā is the ocean of vātsalya.

Vātsalya means love for the poor and the fallen. Just as Śrī Rādhā is an inexhaustible storehouse of amorous rasa, She is also a great ocean of vātsalya-affection.

The writers of the rasa śāstras (aesthetic scriptures) say that the vātsalya rasa is not compatible with the madhura rasa, but Rādhārāṇī makes them compatible in some situations.

For instance, She gives the greatest bliss to Rasika Śiromaṇi (Kṛṣṇa) and Her girlfriends and maidservants when She gives this ‘motherly’ affection to Kṛṣṇa while He takes His meal.
Śrī Rādhā’s vātsalya towards Her girlfriends is also most wonderful. She is always controlled by their affection.

Śrī Rūpa Gosvāmī gives the following example in his ‘Ujjvala Nīlamaṇi’ (Rādhā Prakaraṇa 34):

upadiśa sakhi vṛnde vallabendrasya sūnuṁ
kim ayam iha sakhīnāṁ mām adhīnāṁ dunoti
apasaratu saśaṅkaṁ mandirān māninīnāṁ
kalayati lalitāyāḥ kiṁ na śauṭīrya dhāṭīm

Śrī Rādhā had a quarrel with Śrī Kṛṣṇa, but now She regrets it (this is called kalahāntarita bhāva). She is once more very eager to meet Him, but in order to show that She is under the full control of Her girlfriends, She tells Vṛndā:
“O sakhi Vṛnde! Tell this prince of Vraja that I am controlled by My girlfriends! Why does He waste His words on Me? We are proud girls, it is not proper for Him to stay in our abodes! Tell Him that He’d better fearfully flee! Doesn’t He know the prowess of My friend Lalitā?”

With these words sakhī vatsalā Śrī Rādhā pleases Her girlfriends and gives a hidden instruction to Śyāmasundara to come and meet Her at the same time.

Śrī Rādhā’s vātsalya towards Her maidservants is incomparible!
The maidservants are always showered by waves from the ocean of Her ‘motherly’ affection ! She always keeps them by Her side, calling them “My Rūpa Manjarī, My Rati Ṁañjarī”, with strong feelings of mineness.

In the eighth canto of his ‘Vṛndāvana Mahimāmṛta’, Śrīpāda has drawn a very sweet picture of how Śrī Rādhā showers Her maidservants with the nectar of Her compassion:

kṣaṇaṁ caraṇa vicchedyāc chrīśvaryāḥ prāṇa hāriṇīm
padāravinda samlagna tayaivāharniśaṁ sthitām
preṣṭha dvandva prasāda srag vastra bhūṣādi mohinīm
mahā vinaya sauśilyādy anekāścarya sad guṇām

“Day and night the maidservants are staying at Śrīśvarī’s (Rādhikā’s) lotus-feet, for they will die if they are separated from them for even a second. They are very enchanting as they wear the leftover garlands, dresses and ornaments of the loving divine Couple and they are also adorned with many amazing attributes such as great humility and good behaviour.”

Because there is a lot of the essential part of affection in the vātsalya-ocean, just as yoghurt is the essence of milk, this ocean can be compared to the fifth cosmic ocean, the ocean of yoghurt. (3)

tika to Sri Sri Radha Rasa Sudhanidhi, verse 18