Although Radha had merged into Krushna, She continued to worship Him for the sake of guiding the other gopis. According to the Tantrik and Vaishnavite sects Rukmini representing the Energy of opulence is one of the two Divine Energies (Shaktis) of Krushna while Radha is the Blissful Energy (Ahladini).
The Energy of opulence: ‘When Sudama came to meet Krushna he brought along four handfuls of puffed rice. Even that was borrowed by his wife, from a neighbour. After Krushna had eaten just a pinch of the puffed rice Rukmini snatched it from His hands and said, “We are 16,008 in number. Let us all partake of atleast one grain.” She did this because She knew that if Krushna ate even a pinch, Sudama’s city would turn into gold. So if He were to eat everything then the eight supernatural powers along with the entire wealth from the three regions - earth, nether world and heaven would have to serve Sudama all their lives. So great would be the opulence that he would acquire. Rukmini did this because She was the Energy of opulence rather the deity of wealth, Lakshmi. If a devotee of The Lord has devotion with expectation (sakam) then it is only the Energy of opulence which stops him from acquiring all types of opulence totally.’ - H.H. Kane Maharaj, Narayangaon. In short, the Energy of opulence helps in endowing a devotee having expectation with some opulence while the Blissful Energy imparts the spiritual experience of Bliss to the devotee without expectation (nishkam).
The Blissful Energy: Radha was the Blissful Energy. She never intervened when The Lord endowed someone with riches because Her incarnation was meant for spiritual emotion generated from devotion. Hence that spiritual emotion (bhav) is referred to as Radhabhav. The spiritual emotion of Radha (Radhabhav) or Radha refers to the Adnya chakra.The implied meaning behind this is when a worldly person or a Guru merges into Krushna when carrying out worldly transactions or preaching to disciples respectively they descend to the level of the Adnya chakra.
This stream of spiritual emotion progressing from below upwards in other words is the progress of the devotee towards Self-realisation. Radha being Krushna Himself was a devotee who remained absorbed in Bliss. She certainly does not obstruct someone from being gifted with opulence. Even if God were to endow someone with Bliss She would not stop Him because Her Bliss never declines. The moral behind this is that by giving opulence to others it decreases but Bliss does not. In reality, internally were Rukmini and Radha distinct from each other? Certainly not. But they behaved according to the mission of Krushna’s incarnation. Though they were merged into Krushna they did not become separate because to become separate one needs to have ego.