sadly the only way to get the issue under control is to get animal control and your local shelter involved. the cats will only multiply.
it is kitten season right now, so expect to see a surge in young cats in the next month or two.
un fixed cats are a very very serious problem, a single female and her descendants can produce up to 400,000 cats in a single year !!!!!!
and those cats arent being cared for properly if they are just out roaming around the neighborhood, sorry to say it.
if she finds out its you then tell her you are sorry but you had no choice. let her be upset, id wager that you probally arent the only neighbor who is anoyyed by it...