If you can't say anything nice, don't say anything at all

Nearly five years have passed and in that time I've spoken to my elderly neighbours on 3 occasions. The first time they'd soaked my kitten in water while he was in MY garden. When I confronted them, they denied it, despite the water all over my path and that the old man was holding a hose.
The conversation ended with me saying 'Oh well, whatever!' and him at 40 years my senior, repeating it. Well done, bravo!
Then I think about three years passed and we never spoke. This winter, the guy sprayed my window with anti freeze on a particularly icy day and I thought - ah, hooray, I have a reasonable neighbour again.
Then this evening, I pulled up, and his miserable old bag of a wife said;
"Are you the lady whose garden backs on to ours?"
"yes"
"Can you do something about your brambles?, I keep catching myself"
"Yes, when I have time I will." and I smiled.
She then repeats her same gripe 3 times and I point out she has done so and that I will do it when I have time. She then says she has only just mentioned it and I say, yes, three times in that last sentence.
I said I worked full time and had higher priorities than these brambles and she then started slating my profession and said I was a typical teacher and that she'd known a wrong 'un once.
I said I was doing my best with my busy worklife and she said she did her best as an 'old lady of 76 with a husband who had cancer'. This irritates me because it's hardly the point and I don't appreciate this sort of emotional blackmail over a few thorns. I have done them, but I don't appreciate bullied into it by that sort of thing. That is off.
When I did go out this evening, I cannot work out how on earth she is catching herself and can only conclude she is a damned retard or, a petty minded, pathetic old cow with nothing better to do than moan at me. This surprises me when her husband is so ill. I'm always amazed at people's priorities in these times. You'd think she'd want her neighbours' help, friendship and support. Not to ostricize them. Had she just asked once, politely without slating my career and me generally, I wouldn't be writing this now. But I am.
In the meantime, I will teach children to read and write, learn sign language and become a volunteer.
She can tend to her bloody roses.