Answer: Decentralized structure
Explanation: In simple words, it refers to the organisational structure in which most of the decisions regarding the operations are made by the managers working on mid and lower level. The top managers in such a structure takes only those decisions which are of highest priority to the organisation.
In the given case, Joanna is the lower level managers but still contributes frequently in decision making.
Hence we can conclude that her organisation has decentralized structure.