Explain why her plasma bicarbonate level is so high?

Karen has bulimia, in which she chronically induces vomiting to avoid weight gain. When the doctor sees her, her weight is 89lb and respiration is 6 breaths/min(normal 12)

The results are as follow :

pH 7.61

PCO2 51mmHg

HCO3- is 52mEq/L

Explain why her plasma bicarbonate level is so high? and her Respiratory rate so low?