Try the pillow thing with the couch first and see if she likes it before you invest in anything else. Hannah depends on the pillow to get up because she is too small to jump that high. Since you posted this subject...Now I will be observing her to see why she makes the decision to use a pillow to get down or just take the high dive which she has been doing more of in the past couple of days. (Soon she will probably be jumping up on the couch instead of using the pillows) Have you tried putting snacks on the stairs? Maybe a day or 2 of placing snacks there and there only would get the job done. I'm no pro but am always open to give things a try. The ramp would be cheaper then the floor but then again I do like the floor idea.
I will be checking back to see what others say about this so I can head off the problem before it gets started as I can see it coming very soon!!!