Please Help Me With My Kitty!?

My kitty, Chi-Chi, has just recently started peeing out of her litter box.... she pee's just right outside of it on the floor. She started doing this when she lived at my sister's for a couple months, and when we brought her home she was fine for a couple weeks, but she started doing it again. I don't know what to do, and her time is running out; my dad says we need to take her to the humane society tomorrow.... but that would be heartbreaking because I had her for a while and i love her so much! We tried different types of litter boxes; from open to closed, but she still pee's outside of it. We also keep the boxes very clean, scooping it everyday. Please tell me what to do! Please! Time is running out! D: