I understand that you want to be able to "grab" her instead of "trap" her, and in order to do that you will have to take the next several months gaining her trust. But the red flags that go off in my head about that plan is that she is sure to get pregnant in the meantime. You may already have an unneutered male around, hence the spraying of the neighbor's shrubs. Although spraying can be done by males and females, altered and unaltered, it is most commonly done by unneutered males. While all of us abhor the thought of animals living in cages, an animal under short-term stress usually feels more comfortable in a cage or carrier, because they know they are confined and therefore safe. I know you are having trouble getting your mind around trapping her, it does sound extremely cruel and traumatic, but in this case the means does definitely justify the end. She must be spayed as soon as possible or you will find yourself having to feed, capture, tame, and adopt maybe up to seven cats instead of one. I'm not telling what to do, just giving you another perspective since you are not yet very familiar with cats or feral rescue.