My girlfriend smells very bad and I'm not sure how to tell her?

recently I have been very put off of my girlfriend, her has a terrible odour, it smells slightly like tuna fish mixed with mouldy cheese, she is hygienic so I dont know why? It never used to smell like this. She also has very bad B.O and I don't like being intimate with her anymore, especially since she got feuces on my from doing . Am I mean if I dump her? I don't know what else to do, I don't know how to tell her.