I have a friend, well actually, my neighbor's daughter's cousin's sister, who is moping around the house and no one knows what to do about it, she won't listen to us, so maybe you caj help. Here's the deal. This person, a lovely person, everyone agrees, was, shall we say, involved with a guy, who, long story short, is a d##K, pardon my French. It turns out he was a bully and a cheat, which, to those of us who knew even the littlest bit about him was not a surprise, but no one can ever talk sense to a person who is not in the mood to hear it. Luckily, in our opinions, she gave him the heave-ho. So he promptly takes up with the other woman and parades said woman around. Even though she knows he's a palooka, our friend is still pining for this jamoke. Is there any way we can cheer her up?
In answer to the question you asked. No, All actual cheering up has to be done by the sad person themselves.
In answer to the question you are actually asking, which is, how can we make things better for her instead of worse. I have two thoughts. One is running the guy down isn't going to do much good because she loved him and you don't want to keep harping on her bad taste in guys. So you can't go that route. Second is, she already did what she needed to do, she dumped the guy, so what she is suffering is residual pain, just like when you cut yourself and all the pus and dead cells (yes, I went to school once AND paid attention in class, so what, don't give me gas about it. )form a little net to make all the bleeding stop. Eventually it dissolves and maybe there is a scar, maybe not, but life goes on pretty well. Sometimes lesson learned, like you never try to cut the pit out of that avocado with a sharp knife pointed at your palm again, and sometimes, you forget what you learned and you end up back in the ER. No one can teach these lessons to other people though, you can just be hold their hand while they learn them.