Long and complicated story. Don't want to drip feed so will give it in full, essay form.
My lifelong best friend has been with her DH for 13 years (since they were both 17), married for 5 years.
He works long hours and can be very emotionally neglectful of her. She's cried on my shoulder many times over the years about his other interests (playing sports, gym etc) taking priority over spending quality time with her. She remained faithful all this time and she's not a princess or special snowflake in any way.
The last 18 months have been the worst for her, he's been emotionally unavailable and distant.
She met a guy just over a year ago who swept her off her feet, listened to her problems, flattered her, they shared the same passions in life (art, music etc) and she grew very close to him. Texts, emails mainly but they met up for nights out on a few occasions, physically platonic apart from one occasion where the intensity of the whole thing carried her away and she slept with him. She knows this was wrong and has had to live with the guilt since...and ended the affair shortly after.
She found out halfway through the whole thing that he was shagging his neighbour, a girl who was 'obsessed' with him but that he wasn't that interested in (which makes him sound like a fucking lovely guy) and made her pregnant. He always maintained she wasn't his GF and that he never wanted her, she was just a 'convenience'. Delightful.
The other girl checked his phone...fb, texts, emails etc and saw their exchanges (and the unpleasant things he'd said about her) and went nuts. Contacted my friend's DH via fb, his sister and various associated friends and family members.
She's been like a dog with a bone for the past 6 or 7 months, setting up fake fb and twitter accounts and sending screenshots of their conversations to anyone she thought would listen (me included)...really crazy, violent and dark stuff. She relented for a while round the time she had her baby.
My friend admitted everything to her DH a few months ago and he was devastated but mainly as he understood that it wasn't entirely her fault, that he shared some of the blame. They decided to move on from it and make a go of things. Their communication has been much better and they were starting to heal.
Friend has recently discovered she is pregnant (with her DH's baby) and made a vague announcement on Twitter after her dating scan.
This, it seems, was like a red rag to a lurking-in-the-background-bull and the girl has started harassing my friend and DH again.
I got messages from my very upset friend today asking me to log on to her fb and read the stream of messages she'd received from this girl. It was horrible...full of threats to attack her, wishing ill upon her unborn baby, making vile comments about her appearance etc.
Whilst I absolutely do not condone the affair, I think my friend was reckless and silly, and think the guy is an utter twat in the way he's treated the other girl...in that he and his family support her and the baby financially but take nothing to do with them on a personal level. He's utterly rejected her in the most appalling way. I can understand why she is heartbroken.
My heart is torn in half by what this is doing to my friend. She is being abused, threatened and vilified by this girl. I know she is only lashing out because she wants this arsehole, despite his utter lack of respect or decency towards her and blames my friend for him not wanting her.
Friend and her DH are torn between ignoring her and going to the police. DH doesn't want anyone to know as he wants to protect his wife but they want it to stop. They've offered to meet her or speak on the phone but she has refused, engaging only from behind a keyboard, saying "I just want to ruin your lives like you've ruined mine! You don't get to have a nice life if I can't!"
Can anyone with any knowledge or wisdom advise a course of action?