Those who engage in worship of Srimati Radharani will become very dear to Lord Sri Krishna.
Those who are dear to Lord Sri Krishna are always protected from all dangers.
Radha is considered by the Vaishnava tradition the number one wife of Lord Sri Krishna and that she is even greater than Lakshmi.
It is said in the scripture’s that there are over two billion queens and gopis (cowherd girls) of Lord Sri Krishna, 16,000 are prominent. Out of these, 108 are important, and out of 108, eight are principal. Out of eight gopis, Radha and Chandravali are chief, and out of these two Radha is superior. Radharani’s superiority is given by Krishna’s flute, which repeats the name Radha.
So you can see how special Radharani is to Krishna.
In other Hindu sects, it is said that Srimati Radha and Srimati Rukmini are non-different. One can get closer to Krishna by servicing these Goddesses.
Both of these incarnations of Lakshmi are wives/consorts of Lord Sri Krishna. Both of them display love and devotion to Krishna so much so they lose themselves in Krishna.
This is the example of pure devotional service. It is when one gets lost in Krishna, and can only think of him, how to serve him , where is he, what is he doing…every thought is of God, Krishna.
Both Srimati Radharani and Mother Rukmini display these qualities. Devotees of Krishna always want to serve these two or become like them in service and so they worship them to become like them.