How do I avoid someone I can't stand who wants to be my friend" on Facebook?

This is the sister (call her jen) of a forever friend (call her Mickey) who died a few years ago. Mickey and jen had a terrible childhood with an alcoholic mother who put them in abusive and neglectful situations constantly. Jen got pregnant in high school and married the father, a guy who was gay and stayed in denial for years. She developed one illness after another and became the world's biggest whiner. She was always jealous of my and (aka) Bab's friendship that lasted over 40 years. After some years of bad choices, Mickey married a really super guy who took wonderful care of her to the very end. Mickey's sickness was liver disease brought on by years of alchohol abuse. She got sober too late. Her illness was long, painful and terrible to watch. Her last days, she was aware but asked for us and her sister. She lived in San Diego and we live in Kentucky & Tennessee. Babs and I went. Jen said she was just too sick and too infirmed to go. She was Mickey's only relative. It was awful that she didn't go. I still haven't forgiven jen for being so self involved and letting her collection of mystery illnesses that she allowed to cripple her and keep her from flying out to see her dying sister.

Now Jen wants to be in contact with Babs and I on Facebook . We tried ignoring her and she keeps trying. She even wrote Babs an emal and asked what the problem was. She just doesn't get it. What to do?