Final answer:
The most likely diagnosis for Bella's symptoms is trichomonas. Trichomoniasis is a common sexually transmitted infection caused by the protozoan parasite Trichomonas vaginalis.
Step-by-step explanation:
The most likely diagnosis for Bella's symptoms is trichomonas. Trichomoniasis is a common sexually transmitted infection caused by the protozoan parasite Trichomonas vaginalis. It is characterized by symptoms such as frothy green discharge and fishy odor. Treatment for trichomoniasis usually involves the use of antiflagellate drugs like tinidazole or metronidazole.