Unfortunately Doctor, that logic doesn't mean much to one that can no longer comprehend words. All that Mnemosyne can be certain of right now -- is that something about him is delicious, wanted... And the need to reach him is only getting stronger. This feeling itself is what urges her to push herself off of the wall, intending to propell herself forward with the motion, closer to whatever made him so inviting --

But with poor balance as it was, Mnemosyne was unable to catch herself in time as she reached the other side of the fire escape, tipping over the railing and beginning a long, hard fall, past the Doctor, reaching for him as she zipped by -- and splat onto the cement below.

Face first on the ground, she twitched. No longer able to get up...