Forget it. Just be polite in future when you see them.
I can see why you did it but TBH if my neighbour looked over my fence I would probably react badly too. However I do suffer from a very nosy neighbour who drives me demented & has done for the whole 27 years we have lived here. She is getting worse with age too- she's a lot older than I am & getting very deaf so we do get a bit of privacy in the garden now as she doesn't know if we are out there. We have a huge hedge between us & she yells over it to me if she thinks I am in the garden. It is very thick & she cannot see through it so now I just totally ignore her unless we meet face to face in the front garden. All the other neighbours -who are delightful -ignore her in the main & I am one of the few still on speaking terms with her. (she went to introduce herself to a family who had just moved in & her first question was how much did they earn!!)
So maybe your neighbour has met someone like this in the past & is wary.
How do you acknowledge Easter.
Private care for 'cosmetic' issues