Rudramadevi was nominated as heir apparent and she began to rule the kingdom conjointly with her father as his co-regent from 1259-60 A.D. onwards, under the name of Rudradeva Maharaja.
In the first two or three years of her conjoint rule with her father, the kingdom was thrown into confusion and disorder due to Jatavarma Sundara Pandya I's invasion and the disastrous defeat of the Kakatiyas along with their allies on the battle field of Muttukur near Nellore Though Ganapati was ultimately successful in turning back the tide of invasion, yet he suffered loss of territory end prestige and his hold over his feudatories and nobles was shaken. Under these circumstances, he retired from active politics.
Though Rudramadevi assumed full sovereignty in 1262-63 AD, she was not the crowned queen till the year 1269 A.D.. me date of Kayastha Jannigadeva's Duggi (Palnad Taluk) record The Kakatiyas 143 which speaks of Rudrama as Pattodhriti (queen-designate) of Ganapatideva Maharaja. It was only after the death of her father about the year 1269 A.D., she celebrated her coronation. Rudramadevi's nomination and succession to the throne was not generally approved. Some of the nobles, who were unwilling to submit to a woman's authority took up arms against her Ekamranatha s 'Pratapachantra' refers to her step-brothers Hariharadeva and Murarideva ousting Rudrama, and capturing Warangal, and Rudrama effectively tackling them with the help of the citizens and some of her powerful supporters. However no other evidence is available to prove the existence of her step-brothers. Even if it is believed that some intransigent nobles and near relations rebelled against Rudrama's authority, the Kayastha chiefs Jannigedeva and his younger brothers Tripurari and Ambadeva, Recherla Prasaditya and the Reddi chiefs like Gona Gannaya and a host of others who remained firmly loyal to the queen, espoused her cause and helped her to defeat the rebels.