If she felt like her body was not in good condition, then it would not be worth taking the risk to enter the fighting events, especially if taking such a risk could end up costing her her life.
Participating in the fighting events as Aerial Phantom was already dangerous enough for her, as each time she entered a fight, it could be her last.
If it were not for the experience that could be gained from fighting without restrictions with her life on the line, along with the money that was paid for entering, then not even Ash would be so willing to keep going there under normal conditions.
Both the jobs for Cerberus and the fighting events were dangerous in their own ways, but they provided her with the money she needed and helped her push herself further to gain experiences that she could not gain anywhere else.
