Felicity Bassouls, 67, was accused of sending the rugby star a barrage of e-mails and calls early this year but charges of harassment were dropped in June.
Ben and Abby split up last year and he is now in a relationship with Russian dancer Kristina, who he was paired with during his time on the BBC show in 2013.
Felicity has blasted Ben in a new interview and reveals she spent £12,000 on legal fees fighting the harassment claims. She told the Mail on Sunday: "I think Ben and Kristina are absolutely despicable and should reflect on what they have done.
"I've been to hell and back. I've been used as a pawn and a scapegoat, and I'm not going to pussyfoot around any longer. This is a family feud and this court case was a terrible waste of taxpayers' money.
"The CPS could see that and decided there was no case to answer. I wish Ben had never been paired with that awful person."
Ben, 36, and Abby split after 23 years of marriage a year after his stint on the ballroom dancing show, stating there was no third party involved. Ben and Kristina, 37, have only recently gone public with their relationship and were spotted on holiday in Turkey with Ben’s two daughters this summer.
Felicity claims her daughter asked her to keep her distance last year as the couple worked on their marriage and has been estranged from them ever since.
Her relationship with them has been strained in the past and she claims that in 2008 Ben kicked her out of his and Abby’s home following an argument. Her troubled relationship with her son-in-law finally came to a head when she confronted him about allegedly cheating on her daughter with Kristina in early 2014.
Felicity says she is currently trying to mend her relationships with her family in the hope of spending time with her grandchildren again. She said: "I've asked Abby not to push me away and told her that I love her and want to help. It hurts that she's blaming me when I would do anything to help her - and that's all I've ever tried to do."