However, in retrospect, she was the likeliest vector for the disease that the Founders infected in Odo in order to make him return to the Link.
Clearly the disease was very fast-acting, so it would make sense to assume that the Founders were in a hurry in every respect, including vectoring in the disease. And Odo basically fell ill the moment he touched Arraya.
She need not have been a Founder herself, or even aware of being a vector. But she is still likely to have been a tool of the Dominion.
Timo Saloniemi