It difficult to convince somebody to get back on medication without their full consent. Manic depressive per se are not out of touch of reality. Their thought process are just faster than the average individual.
However, sometimes the manic - depressive (bipolar) patients perform extremely dangerous behaviors that the courts intervene to maintain the safety of the individual and other people and order that medications should be taken by the patient. In these cases, bipolar pts are hospitalized and stabilized with medications.
On the other hand, if the patient is not doing any risky type of behaviors, the difficulty in convincing the patient sets in. I would advise seeking help from all the trusted friends/family the patient has to assist you in this difficult task. You may want to monitor her closely that she does not hurt herself or others during these manic periods.