Mine used to do stuff that could be described away as a bit strange but nothing more sinister - she would never agree to drive to collect / deliver the children but when a letter arrived to her house addressed to her and my DP she drove all the way to hand deliver it to me. It turned out to be a letter from their DD's he didn't need as they had discussed it on the phone that day and he had been emailed a copy. Or she would tell the children she invited me or both of us to their events but I said I wasn't interested (I would be completely in the dark).
There were plenty of these minor incidences and when I'd mention it he would say she was trying to wind me up. I thought he was being ridiculous - I laughed and said that he was being a typical man convinced that women are bitchy and always competing for status or whatever. His ex never stopped bossing him but I stayed out of it as much as possible; not my circus. She was really upright and awkward around me but that was fine too, who wants to be friends with the next partner?
Then she started dropping things to the house; a laptop, memory drive saying there were photos of the kids my DP might like on them. I was getting irritated with him allowing her drop things off as I was on a cleanup mission and asked him why he hadn't taken the photos off. He ignored the devices then just delivered them back to her office saying he didn't want them.
He would often say to me - you don't know what she's like, this is all about control. Ignore all this stuff, don't fall for it. I thought he was being totally ridiculous, the woman just wanted everyone to move on.
In the background his ex was developing a close friendship with his sister that reportedly had never been there before and getting very involved with his family. This bothered my DP but it's a free world.
We were in the process of buying a house. All of a sudden we reached an impasse. We needed a document from the ex (regarding shared property) and she wouldn't supply it. She wouldn't answer calls and employed various delaying tactics. The owner threatened to cancel the sale. I bumped into her and tried to explain (I assumed there was some sort of misunderstanding). She laughed. I was speechless.
After the devices had been returned without a reaction, envelopes began being delivered with the children. They contained very intimate or romantic photos. I was gutted when I saw them. Then the text messages began - any excuse to make up accusations or tell me my DP would never move on from her.
Horrible lies were fed through his family and came back to me. Thankfully i knew them to be untrue as the facts didn't add up but she could have sowed some doubt if circumstances had been different.
I told her to stay away unless there was an emergency with the children and I blocked her.
DP continued to ignore her.
Then the (teenage) children began to throw accusations at him; why did he not pay maintenance, why was he making plans to emigrate with me leaving them behind, why had he been unfaithful. All lies, each and everyone of them.
We are getting married next year (delayed due to multiple factors) and I expect a ramp-up of disruption from her in the lead-up to the date. When our child was born, she made sure the weekend (I had a planned C-section so gave her the date in advance) had everyone running around after her.
She ended the marriage and has a new partner. There were no infidelities. She doesn't want him back afaik. I reckon she just needs to believe that everything spins around her.