There are people who can represent themselves in court, even in murder cases, so why can't Britney herself request the conservatorship be terminated by the court? She needs to go above this level of the courts even if it means to go in front of the supreme court.
JMO MOO IMO
Technically, she can't make an application, hire a new lawyer or retain her own mental health professionals because at this time, she's considered legally incompetent.