I agree that you could be saving Lucy from being bred from. You've done a good thing.
Whilst I am not a 'desex at all cost' person, I acknowledge that it is a personal decision that should be made after all risks, conditions and scenarios are evaluated.
Personally, I have always desexed all my animals between 6 - 12 months and earlier if they are a feline. It works for me.
I am 100% against legislation though that forces people to desex. Yes, there are bybers and puppyfarmers and people who let their dogs have puppies and then dump them, but these people make up probably only about 0.05% of the dog owning population, so why tar everyone with the same brush?
Most dog owners are responsible and loving.