Help!!! Question about my cat?

About a week or two ago I took my cat to the vet because she looked sick. She had stuff coming out of her mouth and the outside of her nose was bleeding. The vet told us that her tongue was infected so they gave us some antibiotics that we have to give to her twice daily. She is Suppose to go to the vet for a check up, but my dad dosnt want to because we already spent close to $400 on the last vet visit. So now she looks and is acting alot better, but I was just wondering when it is alright to take the cone off of her head.