Answer: Advocate
Step-by-step explanation: In simple words, advocate level is the topmost stage in the loyalty ladder. In this stage, the customer gets used to for the brand and along with repurchasing it he or she also works as a promotional toll for the brand.
In the given case, Maria has been repurchasing the products from the firm and is also praising the brand online. Hence we can conclude that she is on the advocate rung.