The only person who Mei might beat is Hidan IF she keeps Hidan at a distance with her lava abd boil style. She might be Konan aswell. just.....maybe...hmm....
She can beat Hidan-Mist will blind him, acid will melt him.
Third Kazekage-Mist will blind him, acid will melt him and his puppets.
Fourth Kazekage-same as above.
she can beat some of them. it's just that all of her feats are against edo madara, so she's not really going to shine. but she has really tough area of effect techniques, that lava of hers forced madara into susanoo right off the bat, she isn't mizukage for nothing.