Well, I'm already trying to come up with a solution that will make things easier for her. Usually she's climbing onto my desk and from there, she'd jump onto the window sill (and back). Looks difficult, but for some reason, it seems to be easier for her. (I took some pictures of this earlier today and will post them later to show you). And yes, a spray bottle for Lily is definitely an option!
Besides, she seems to be feeling a little better today, and she was happy about her Sheba meal we had left from her birthday present. :-) She was running very fast when I served her food earlier today.