I never used the spray stuff so can't comment, but if that doesn't work you could try SSCAT
, which is a motion sensitive device that emits a blast of canned air (so totally harmless, but scary to a cat) when something enters range.
Another option might be to cover the lower part of the window with a frosted film so that she can't see the other cat, but it still lets light in.
I had a similar situation with the neighbor's cat climbing on the railing of my front steps and peering through my living room window. It drove one of my cats absolutely insane and he would throw himself at the window trying to get at him, then re-direct his aggression to his fellow housemates. I had to zip-tie a sheet of plastic to the railing to prevent the other dude from jumping up on it.