Not fleas then what?

Hello again! My tiger has been scratching her little tail off for the past 4 days all of the sudden. I assume she has fleas even though i dont see any (we live on the 3 floor of an apt. building and she does go out on the balcony from time to time) i just figured she might have goten them from the trees maybe, i dont know, can fleas hop from the ground to the trees :? . Anyway i found something on dangerous house plants in relation to cats, and the plant i have was on the list (Philidendron,i think u spell it that way) coincidently tiger has been hanging around this plant for the past week or so, i would yell NO! and later she woud be back, i checked it out and i dont really see any bite marks, but i see where she was picking in the dirt. SOOO im wondering is she having a allergic reaction to this plant.What do you think? Bye the way she is going to the vet Sat.